greylist.conf man page

greylist.conf — milter-greylist configuration file

Description

greylist.conf configures milter-greylist(8) operation. The format is simple: each line contains a keyword and optional arguments. Any line starting with a # is considered as a comment and is ignored. Blank lines are ignored as well. Comments at the end of lines are accepted in some situations, but do not take them as granted. A statement can be continued on the next line by using a backslash. Anything after the backslash will be ignored.

Whitelist

The primary use of greylist.conf is to setup milter-greylist(8) whitelist. It also offers a handy blacklist feature. Access-lists (ACL) are used to do that. ACL enable the administrator to specify complex conditions on sender IP, sender DNS address, sender e-mail address, and recipient e-mail address. If support for Dnsrbl was built-in, it is even possible to use Dnsrbl in ACL.

An access-list entry starts with the racl keyword followed by an optional id quoted string, then the greylist, whitelist, blacklist, or continue keyword, and by any set of the following clauses: addr, domain, from, rawfrom, rcpt, rcptcount, helo, sm_macro, time, auth, tls, spf (if build with SPF support), geoip (if build with GeoIP support), p0f (if build with p0f support), ldapcheck (if build with --with-openldap), urlcheck (if built with --with-libcurl), dnsrbl (if built with --enable-dnsrbl), and nsupdate (if supported by the DNS resolver). A message will match an ACL entry when it complies with all of its clauses.

The greylist, whitelist, and blacklist keywords will cause the message to be respectively greylisted, accepted or rejected if all ACL clauses match, and ACL evaluation is terminated there. If an ACL with continue keyword does match, nothing is decided and next ACL are evaluated.

Clauses can be negated, by prefixing them by the not keyword. Here is the detail of all possible clauses.

addr

This clause is used to specify a netblock of source IP addresses. The syntax is an IP address followed by a slash and a CIDR netmask. Here is an example:

racl whitelist addr 127.0.0.0/8
racl whitelist addr 192.168.3.0/24
racl whitelist addr ::1

If the netmask is omitted, /32 is assumed for an IPv4 address and /128 is assumed for an IPv6 address.

You should at least whitelist localhost (127.0.0.1/8), and if you have some user clients connecting to the machine, you should whitelist the addresses they connect from if you don't want them to get error messages when sending e-mail.

domain

This clause selects source machines based on their DNS name, performing a suffix search. For instance, this will whitelist any machine in the example.net domain:

racl whitelist domain example.net

Suffix search matching means, for example, that gle.com will match google.com. If you want domain names to match on subdomain boundaries (e.g. gle.com will match mail.gle.com and gle.com but not google.com) then enable domainexact

The name resolution is made by Sendmail, which hands it to milter-greylist(8). As a result, it is impossible to use DNS aliases here. On the other hand, this will work even if your DNS resolver is not thread-safe.

from

This is used to select sender e-mail addresses You should not use that feature, because sender e-mail addresses can be trivially forged.

Please note that the sender e-mail is cleared from spaces and anything leading an equal (=) sign so that mailing-lists return-address with unique return paths can still match. If you need unedited sender address, use a rawfrom clause.

Here is an example:

racl whitelist from postmaster@example.com

rawfrom

Same as from but the sender e-mail address is not modified to stip anything. rcpt This is used to select recipient addresses. Example:

racl greylist rcpt John.Doe@example.net

rcptcount

Followed by an operator and a recipient count, this is used to select the amount of recipients. Example:

racl blacklist rcptcount >= 25 msg "No more than 25 recipients, please"

helo
Followed by a quoted string or a regular expression, this can be used to filter on the HELO string.
sm_macro
This is used to select a Sendmail macro value. See the section on that topic for more information.
time

This is used to specify a time set. It should be followed by a quoted string of crontab(5)-like time specification. Here is an example that whitelists mail addressed to a single recipient during office hours (from 8:00 to 16:59 from monday to friday):

racl whitelist time "* 8-16 * * 1-5" rcpt info@example.net

geoip
This is used to specify a country, as reported by GeoIP. The country code must be upper case, and is only available if milter-greylist was built with GeoIP support. Special country code ZZ is used when the country cannot be determined (this happens for private addresses, for instance). The geoipdb statement can be used to specify the location of GeoIP database. geoipv6db statement can be used to specify the location of GeoIPv6 database.
p0f
This is used to match against the remote system OS fingerprint genre and detail,obtained from p0f. It is only available if milter-greylist was built with p0f support. p0f clauses can be used with a quoted string for case-insensitive substring match, or against regular expressions. The p0fsock statement can be used to specify the location of the p0f socket.
auth

This is used to select a user that succeeded SMTP AUTH. In order to select any user that succeeds SMTP AUTH, you can use a regular expression matching, like below;

racl whitelist auth /.*/

Using such a clause automatically disable global STARTTLS and SMTP AUTH whitelisting, like if the noauth keyword would have been used.

tls
This is used to select the distinguished name (DN) of a user that succeeded STARTTLS. Using such a clause automatically disable global STARTTLS and SMTP AUTH whitelisting, like if the noauth keyword would have been used.
spf

This is used to test SPF status. Possible values are pass, softfail, fail, neutral, unknown, error, none, and self. The first seven values are plain SPF validation status. The self value is a special test that checks the server's local IP address against the sender's SPF record. If that test validates, odds are good that the sender SPF record is wide open, and this is hint that SPF should not be trusted.

In order to use spf self, Postfix users must specify the local address in the configuration file, using the localaddr option.

Absence of any value after the spf keyword is a synonym for spf pass. This is present for backward compatibility.

The spf clause is only available if SPF support was compiled in. Using it will disable global SPF whitelisting, like if the nospf keyword would have been used.

ldapcheck
This is used to query an LDAP directory. See the section on that topic for more information.
urlcheck
This is used to query an external configuration source through an URL. See the section on that topic for more information.
dnsrbl
This is used to select a Dnsrbl. See the section on that topic for more information.
nsupdate
This always-matching clause performs a DNS update, see the section on that topic for more information.

The domain, from, and rcpt clauses may be used with regular expressions. The regular expressions must be enclosed by slashes (/). No escaping is available to provide a slash inside a regular expression, so just do not use it. Regular expressions follow the format described in re_format(7). Here is an example:

racl greylist rcpt /@example\.net$/

When regular expressions are not used, from, and rcpt perform a case insensitive substring match with leading and trailing brackets, spaces and tabs stripped out. domain performs a case insensitive suffix match. This means, for example, that gle.com will match google.com. If you want domain names to match on subdomain boundaries (e.g. gle.com will match mail.gle.com and gle.com but not google.com) then enable domainexact

An ACL entry can also hold various optional parameter used on match: delay, autowhite, flushaddr, nolog, code, ecode, report, maxpeek, addheader, addfooter, and msg

delay
Specify the greylisting delay used before the message can be accepted. This overrides the greylist global setting, and it only makes sense on an racl greylist entry.
autowhite

Specify the autowhitelisting duration for messages matching this ACL. This overrides the autowhite global setting, and it only makes sense on an racl greylist entry. Example:

racl greylist rcpt JDoe@example.net delay 15m autowhite 3d
racl greylist rcpt root@example.net delay 1h autowhite 3d

flushaddr

If a message matches the rule, any entry in the greylist or autowhite databases matching the sender IP is removed. Used with a Dnsrbl blacklist ACL, it is useful for freeing the database from entries set up by a machine which is known to be a spammer. Example:

racl blacklist dnsrbl "known-spammer" flushaddr

nolog

Do not generate syslog message if this rule matches. Example:

racl whitelist default nolog

code
ecode
msg

These 3 values can be used to choose the SMTP code, extended code and reply message for temporary failures and rejects. Example:

racl blacklist dnsrbl "spamstomp" msg "IP caught by spamstomp"
racl greylist default code "451" ecode "4.7.1"

The msg strings accepts format string substitution as documented in the Format Strings section. For instance, %A gets substituted by the ACL line number.

None of the last 3 values makes sense for a whitelist entry.

report
This value overrides the text displayed in the X-Greylist header, for messages that milter-greylist(8) lets pass through, either because they are whitelisted, or because they passed greylisting (see Reporting). This string can be substituted as documented in the Format Strings section.
maxpeek
This parameter only makes sense in a RCPT-stage ACL. It overrides the global maxpeek setting for DATA-stage handling of the message. It has no effect if global maxpeek is set to 0.
addheader

This quoted string is a RFC822 header that gets added to the message. Format string substitution is supported. No check is done for header length standard compliance, so make sure the substituted string is shorter than 2048 characters. Headers are appended to the bottom, unless an optionnal comma-separated positive index is specified after the quoted string; in this case the header will be inserted at this index point from the top. Here is an example:

racl continue addheader "X-Personnal-Header: Hello world!",1
addfooter
Append a footer to the message. Usual escape sequences such as \n can be used to get special characters. The string is subject to format string expantion as described in the Format Strings section. The footer will not be append if milter-greylist was not able to capture the whole message, therefore maxpeek must be set approriately.

Entries in the access-list are evaluated sequentially, so order is very important. The first matching entry is used to decide if a message will be whitelisted or greylisted. A special default clause can be used in the last ACL entry as a wildcard. Here are a few complete ACL examples:

Example 1:

racl whitelist from friend@toto.com rcpt grandma@example.com
racl whitelist from other.friend@example.net rcpt grandma@example.com
racl greylist rcpt grandma@example.com
racl whitelist default

Example 2:

racl whitelist addr 193.54.0.0/16 domain friendly.com
racl greylist rcpt user1@atmine.com
racl greylist rcpt user2@atmine.com
racl greylist rcpt user3@atmine.com
racl whitelist default

Example 3:

racl whitelist rcpt /@.*otherdomain\.org$/
racl whitelist addr 192.168.42.0/24 rcpt user1@mydomain.org
racl whitelist from friend@example.net rcpt /@.*mydomain\.org$/
racl whitelist rcpt user2@mydomain.org
racl greylist rcpt /@.*mydomain\.org$/
racl whitelist default

Data-Stage Acl

ACL using the racl keyword are evaluated at the RCPT stage of the SMTP transaction. It is also possible to have ACL evaluated at the DATA stage of the SMTP transaction, using the dacl keyword, provided the message went through RCPT-stage ACL, and possibly greylisting. Note that you cannot use the greylist action at DATA-stage if the RCPT-stage ACL that matched had a greylist action itself. The following clauses can be used to work on message content:

dkim
DKIM status (if build with DKIM support). Possible values are pass, fail, unknown, error, and none,
header
String or regular expression searched in message headers
body
String or regular expression searched in message body
msgsize

Operator followed by a message size (k or M suffix allowed for kilobytes or megabytes). Example:

dacl blacklist msgsize >= 4M msg "No more than 4 MB please"

spamd

SpamAssassin score (if build with SpamAssassin support). If used without comparison operator spamd is true if the score is above threshold. The spamdsock keyword can be used to specify the location of the spamd socket.

Example 1:

spamdsock unix "/var/spamassassin/spamd.sock"
racl whitelist default 
dacl greylist spamd

Example 2:

spamdsock inet "127.0.0.1:783"
racl whitelist default 
dacl blacklist spamd > 15 msg "Your message is considered spam."
dacl greylist  spamd > 10 delay 2h
dacl greylist  spamd > 5  delay 1h

Note that if there are multiple recipient, a rcpt clause at DATA stage evaluates to true if it matches any of them. If you want to match an exact set of recipients, you can use multiple rcpt clauses along with a rcptcount clause.

Lists

It is often useful to group several users or sender IP addresses in a single ACL. This can be done with lists. Lists must be first defined and given a name before they can be used in ACL entries. Here is an example:

list "my users" rcpt { user1@example.com user2@example.com }
list "local" addr { 192.0.2.0/24 10.0.0.0/8 }

racl whitelist list "local"
racl greylist list "my users"
racl whitelist default

Backward Compatibility

Previous versions of milter-greylist(8) used addr, domain, from, and rcpt lines, without the racl keyword. Access-list management is intended to replace them. These lines are still accepted by milter-greylist(8), but they are deprecated. milter-greylist(8) handles them as access-list entries with a single clause. They are added at the head of the access-list so the use of these keywords and access-lists may lead to unspecified behaviour. Do not mix them.

test mode (using -T) is also deprecated. Access-list semantics do not depend on this flag.

milter-greylist(8) also used to only have a RCPT-stage ACL, which was configured through acl statements. These have been replaced by racl statements (as opposed to dacl statements for DATA-stage ACL). acl statements are still accepted for backward compatibility and are a synonym for racl statements.

Mx Sync

Synchronization of the greylist among multiple MX is configured using the peer keyword. List each other MX IP addresses using the peer keyword. Here is an example:

peer 192.0.2.18
peer 192.0.2.17
peer 192.0.2.22 timeout 7
peer 192.0.2.38 timeout 5m

You can list the local machine in the peer statements, it will be ignored.

The timeout clause sets a peer communication timeout to have proper retrial in case of slow MX peer. The default value is 3 seconds. The special value of 0 disables the connection retrials.

By default, milter-greylist will listen on all interfaces using TCP port 5252 or the port number given by service named mxglsync if defined in /etc/services or other directory service. This behaviour can be changed by using the syncaddr keyword. Here are a few examples:

syncaddr *
syncaddr * port 7689
syncaddr 192.0.2.2 port 9785
syncaddr 2001:db8::1:c3b5:123
syncaddr 2001:db8::1:c3b5:123 port 1234

Using '*' as the address means to bind to all local interfaces' addresses. Note that if you are not using the default port, all MXs must use the same port number.

For outbound connections the system is selecting one of the possible addresses. If you want to use a specific IP you can use:

syncsrcaddr 123.456.78.9

Text Dump

milter-greylist(8) uses a text dump of its database to resume operation after a crash. The dump is performed at regular time interval, but as it is a heavy operation, you might want to configure a particular time interval, using the dumpfreq option.

If the dumpfreq value is too small, it will kill performance. If it is too high, you will loose a bigger part of the database on a crash.

Set dumpfreq to 0 to get a dump on each change (kills performance), Set it to -1 to never dump to a file (unsafe as you lose the whole greylist on each crash), or give a time value for the delay between dumps. The time is given in seconds, except if a unit is given: m for minutes, h for hours, and d for days.

You may further improve the performance of the dump operation at the expense of humanly readable timestamp which by default appears as a comment at the end of each line in the dumpfile. You may disable generation of this comment by specifying dump_no_time_translation option in the configuration file. This is specifically recommended if your dumpfile grows to 100's of megabytes - it can reduce the time needed for the dump operation by the order of magnitude!

Reporting

By default, milter-greylist(8) will add a X-Greylist header to any message it handles. The header shows what happened to the message: delayed or not delayed, and why. The following options can be used in greylist.conf to alter this behavior:

report none
Never add a X-Greylist header.
report delays
Only add a header if the message was delayed.
report nodelays
Add a header if the message was not delayed. The header explains why the message was not delayed.
report all
Always add a header. This is the default.

Sender Callback Systems

Sender callback systems are another anti-spam measure that attempts to send a DSN to the sender address before accepting a message. If that fails, then the sender address is wrong and the message is rejected. Such systems usually stop their callback check at the RCPT stage of the SMTP transaction.

Greylisting temporarily rejects at the RCPT stage, so sender callback and greylisting love to fight each other. milter-greylist(8) proposes a workaround to that problem with the delayedreject option. For messages coming from <> (that is, for DSN), it will cause the temporary reject to happen at the DATA stage of the SMTP transaction instead of the RCPT stage. That way, milter-greylist(8) will cope much better with sender callback systems.

This has a minor drawback (and this is why it is not enabled by default): for a multi recipient DSN, whitelisted recipient will not be honoured: the message will be delayed for everyone.

Sendmail Macros

Any sendmail macro can be used as a clause in the access list. You need to define a (macro, value) pair using the sm_macro keyword before using it. Here is an example that uses the {client_resolve} macro to apply a larger greylisting delay to hosts that have a bogus reverse DNS:

sm_macro "maybe_forged" "{client_resolve}" "FORGED"

racl greylist sm_macro "maybe_forged" delay 1h
racl greylist default delay 15m

A regular expression can be used as the macro value. It must be surrounded with slashes and not by quotes. The special value unset can also be used to match an unset macro:

sm_macro "not_foo" "{foo}" unset

Note that any Sendmail macro that is not exported using the Milter.macros.envrcpt setting of sendmail.cf will be seen as unset from milter-greylist.

Dnsrbl

DNS Reverse Black List can be used to toggle an ACL. They must be defined and named before they can be used. Here is an example which uses a bigger greylisting delay for hosts caught in the SORBS dynamic pool DNRSBL (this will include DSL and cable customers pools, which are well known to be massively infected by spamwares):

dnsrbl "SORBS DUN" dnsbl.sorbs.net 127.0.0.10/32

racl greylist dnsrbl "SORBS DUN" delay 1h
racl greylist default delay 15m

The definition of a Dnsrbl starts by the dnsrbl keyword, followed by the quoted name of the Dnsrbl, the DNS domain on which addresses should be looked up, and the answer we should consider as a positive hit.

Dnsrbl support is only available if enabled through the --enable-dnsrbl config flag. Please make sure milter-greylist(8) is linked against a thread-safe DNS resolver, otherwise it shall crash.

DNS updates

ACL are able to trigger a DNS update, which can be used to feed a Dnsrbl. That functionnality is enabled at build time if the DNS resolver has DNS update support.

Configuration is done with the nsupdate statement, which may be used several times, and the optionnal tsig statement, if you want ot use authenticated DNS update. Here is an example syntax:

tsig "dns-update" "hmac-md5" "1B2M2Y8AsgTpgAmY7PhCfg=="
nsupdate "bl.example.net" { rname "%j.bl.example.net" rvalue "127.0.0.2" tsig "dns-update" }

The options for nsupdate are:

rname
Created record name, which uses format strings.
rvalue
Created record value, which uses format strings.
servers
Quoted comma-separated list of DNS server the update should be sent to. Default is to use the system confifugration, usualy from /etc/resolv.conf
ttl
TTL of created DNS record. Default is 0 seconds.
class
Created record class, as numeric value. Default is 1, for IN class.
type
Created record type, as numeric value. Default is 1, for A type.
tsig
The name of a tsig configuration, which must have been supplied before. If unspecified, unauthenticated DNS updates are performed.

Once configured, DNS updates can be used in any ACL:

racl blacklist rcpt spamtrap@example.net nsupdate "bl.example.net"

Properties

Properties are variables that can be set, evaluated and printed in ACL. A property may be dropped once the current recipient is processed, or it can be retained until the message is processed. They can be created through the following always-matching ACL clauses:

set $name="value"
This sets a property that will be retained for all next recipients. Right hand side of the clause may be a quoted string (which will be substituted using format strings, as described in the Format Strings section), a number, or another property name (which will be substituted by the property value).
rset $name="value"
Same as set clause, except that the property will be droped once the current user will have been processed.
urlcheck
These clause will cause properties to be fetched from an external web service. See the URL checks section below for details.
ldapcheck
These clause will cause properties to be fetched from a LDAP directory See the LDAP Checks section below for details.

Properties can be used as left-hand side part of ACL clauses:

racl blacklist $name "badvalue"
racl blacklist $name /badregex/

If used left-hand side and prefixed by a star, the property will be evaluated as a glob(7) pattern, In the example below, if sender DNS domain is test.example.net and $domain is *.example.net, we get a match.

racl blacklist *$domain "%f"

They are also available as right-hand side of many ACL clauses:

racl continue set $badword="spam"
racl blacklist body $badword

Values of properties can be obtained in any quoted string that is subject to format string expantion:

racl continue set $webmaster="webmaster@example.net"
racl blacklist domain evil.net msg "blacklisted, ask $P{webmaster} why"

When the property value is a number, it can be increased or decreased using this syntax:

racl continue set $score+=5
racl continue set $score-=5

Here again, right hand side may be a quoted string, a number or another property. For the quoted string and property cases, a conversion is first made to an integer, using 0 as a value on failure. Note that no arithmetic evaluation occurs. For instance, the quoted string "1 + 1" will be evaluated as 0.

The log ACL clause can be helpful when one need to figure what happens to property values during the ACL flow. See the CUSTOM REPORT section for more details.

URL checks

milter-greylist(8) is able to query external sources of information through various URL, if it was built with --with-libcurl. Here is an example:

urlcheck "glusr" "http://www.example.net/mgl-config?rcpt=%r" 5

racl greylist urlcheck "glusr" delay 15m
racl whitelist default

The trailing 5 at the end of the urlcheck definition is the maximum number of simultaneous connections we want to launch on this URL. For each message, the URL will be queried, with % format tags being substituted. For instance, %r is substituted by the recipient. See the Format Strings section for the complete list of substitutions.

milter-greylist(8) expects an answer containing a list of \n terminated lines, with key: value pairs. The most basic answer to get a match is:

milterGreylistStatus: Ok

TRUE can be used as an alias for Ok here.

The answer can be more complex, with keys that will overload the ACL settings:

milterGreylistDelay
The greylisting delay to use (time unit suffix allowed).
milterGreylistAutowhite
The autowhite delay to use (time unit suffix allowed).
milterGreylistFlushAddr
The value is ignored. If this key is present, then the IP address for the sender machine will be flushed from greylist and autowhite databases.
milterGreylistCode
The SMTP code to return (e.g.: 551).
milterGreylistECode
The SMTP extended code to return (e.g.: 5.7.1)
milterGreylistMsg
The string to return with SMTP codes.
milterGreylistReport
The string to display in the X-Greylist header.
milterGreylistIgnore
This line will be ignored, without warnings in the logs.
milterGreylistAction
This feature is nifty but use it with caution, as it makes the access list a bit difficult to understand. By specifying the values greylist, whitelist, or blacklist, it is possible to overload the ACL action itself.

The ACL will match if any of the above key is returned: milterGreylistStatus is not mandatory.

Optional keywords can be appended to a urlcheck definition:

postmsg

On DATA-stage ACL, This causes the message to be sent (up to maxpeek bytes) in a POST request. Here is an example:

urlcheck "extfilter" "http://www.example.net/f.cgi" 5 postmsg

dacl blacklist urlcheck "extfilter"
dacl whitelist default

getprop
Gather the properties returned by the URL and reuse them in the ACL. The gathered properties can be accessed in the current and following ACL by prefixing them by a dollar ($).
clear
This causes gathered properties to be cleared on each new recipient. This avoids properties for several recipients to mix.
fork
Tells milter-greylist(8) to fork a separate instance of itself for performing the queries. Use it if you encounter thread-safety problems. fork is not compatible with postmsg.
domatch
Cause the ldapcheck clause to be evaluated in ACL. Default behavior is to ignore the result and just fecth properties, except if the LDAP directory is unreachecable, in which case a temporary failure occurs. The fixldapcheck gloabal settings may also be used to globaly cause all ldapcheck and urlcheck clauses to match.

Here is an example that will use various Dnsrbl depending on a per-recipient setting stored in the dnsrbl attribute of a LDAP directory.

dnsrbl "RBL2" "rbl.example.net" "127.0.0.2"
dnsrbl "RBL3" "rbl.example.net" "127.0.0.3"
dnsrbl "RBL4" "rbl.example.net" "127.0.0.4"
urlcheck "userconf" "ldap://localhost/dc=example,dc=net?milterGreylistStatus,dnsrbl?one?mail=%r" 5 getprop clear

racl blacklist urlcheck "userconf" $dnsrbl "RBL2" dnsrbl "RBL2"
racl blacklist $dnsrbl "RBL3" dnsrbl "RBL3"
racl blacklist $dnsrbl "RBL4" dnsrbl "RBL4"

Note that when matching gathered properties, format strings and regex can be used.

LDAP Checks

If milter-greylist was built with --with-openldap, then you can also use ldapcheck for pulling information from an LDAP directory. This works exactly like urlcheck, except that properties are always collected: The getprop option is implicit.

A list of LDAP URL to use can be specified with the ldapconf keyword. The network timeout is optional.

ldapconf "ldap://localhost ldaps://ldap.example.net" timeout 2s

When ldaps:// is used, the system's ldap.conf file is used to locate x509 certificates.

When defining LDAP queries with the ldapcheck statement, note that the scheme and host part of the URL are ignored. Servers listed in ldapconf are used instead.

Rate Limit

The ratelimit keyword specifies a ratelimit configuration to be used in access lists. It must be followed by the rate limit configuration name, what is being accounted (i.e.: session for SMTP sessions, rcpt for recipients, data for bytes in body and headers), the actual limit, and the sampling period. Example:

ratelimit "internalclients" rcpt 10 / 1m

racl blacklist addr 192.0.2.0/24 ratelimit "internalclients" \ msg "you speak too much"

The ratelimit keyword can also have an option key statement, which determine the set of key for message accounting. The default is %i for per IP address accounting (see the Format Strings sections for the possible syntax of this field). Here is an example that configures a rate limit of 100 messages per hour for each individual recipient-IP set.

ratelimit "internalclients" rcpt 100 / 1h key "%r%i"

racl blacklist addr 192.0.2.0/24 ratelimit "internalclients" \ msg "you speak too much"

Custom Reports

The stat keyword can be used to specify a custom report for milter-greylist activity. It should be supplied with an output (either file or external command) and a format string. Here is an example:

stat ">>/var/log/milter-greylist.log" "%T{%T},%i,%f,%r,%A\n"

If the output starts by >> or > then it is a file. Use >> to append to an existing file, and use > to overwrite it. If the output starts by a | then the output is a shell command, like in the example below:

stat "|logger -p local7.info" "%T{%T},%i,%f,%r,%A\n"

The format string gets substituted as URL checks format string: %r gets substituted by the recipient, %f by the sender, and so on. See the Format Strings section for a complete list of available substitutions.

There is also an always-matching log ACL clause that can be used to send a formated string to syslog with LOG_INFO level. Here is an example:

racl continue rcpt /@example\.com$/ log "I was here"

Command-Line Flag Equivalents

Most milter-greylist(8) command-line options have equivalent options that can be set in the configuration file. Note that if a command line option is supplied, it will always override the configuration file.

If a command-line equivalent keyword is used more than once, the last keyword will override the previous ones.

verbose
Enable debug output. This is equivalent to the -v flag.
quiet
Do not tell clients how much time remains before their e-mail will be accepted. This is equivalent to the -q flag.
nodetach
Do not fork and go into the background. This is equivalent to the -D flag.
noauth
Greylist clients regardless if they succeeded SMTP AUTH or STARTTLS. Equivalent to the -A flag.
noaccessdb
Normally milter-greylist(8) will whitelist a message if sendmail(8) defines a ${greylist} macro set to WHITE. This enables complex whitelisting rules based on the Sendmail access DB. This option inhibits this behavior.
nospf
Greylist clients regardless if they are SPF-compliant. Equivalent to the -S flag.
testmode
Enable test mode. Equivalent to the -T flag. This option is deprecated.
greylist

The argument sets how much time milter-greylist(8) will want the client to wait between the first attempt and the time the message is accepted. The time is given in seconds, except if a unit is given: m for minutes, h for hours, and d for days. The greylist keyword is equivalent to the -w option. Here is an example that sets the delay to 45 minutes:

greylist 45m

autowhite

This sets the auto-whitelisting duration, equivalent to the -a command-line option. As for the greylist keyword, units can be supplied. Here is an example for a 3 day long auto-whitelisting:

autowhite 3d

pidfile

This causes milter-greylist(8) to write its PID into the file given as argument, like the -P command line argument does. The path to the file must be absolute and it must be enclosed in quotes. Here is an example:

pidfile "/var/run/greylist.pid"

dumpfile

This chooses the location of the greylist dump file, like the -d command line option does. The path must be absolute and enclosed in quotes. It can optionally be followed by an octal permission mode. Example:

dumpfile "/var/lib/milter-greylist/db/greylist.db" 640

subnetmatch

This is equivalent to the -L command line option. It takes a slash followed by a CIDR mask as argument, and it commands the subnet matching feature. Example, for a class C wide matching:

subnetmatch /24

subnetmatch6

This is equivalent to the -M command line option. It takes a slash followed by a prefixlen as argument, and it commands the subnet matching feature. Example, for a subnet wide matching:

subnetmatch6 /64

socket

Like the -p command line option, this keyword is used to specify the socket used to communicate with sendmail(8). It must be enclosed in quotes and can optionally be followed by an octal permission mode (valid values are 666, 660 or 600, other values cause an error):

socket "/run/milter-greylist/milter-greylist.sock" 660

user

This keyword should be followed by a quoted user login and optionally a colon followed by a groupname. Like the -u option, this is used to run milter-greylist(8) as a non root user. Here is an example:

user "smmsp"

Miscellaneous

These options have no command line equivalent:

logfac
Sets the syslog facility for messages. Can be set to any of the standard facilities: kern, user, mail, daemon, auth, syslog, lpr, news, uucp, cron, authpriv, ftp, local0, local1, local2, local3, local4, local5, local6, local7. Can also be set to none to disable syslog output completely.
timeout
is used to control how long greylist tuples are retained in the database. Value is in seconds, except if a suffix is given (m for minutes, h for hours, d for days). Default is 5 days.
extendedregex
Use extended regular expressions instead of basic regular expressions.
unbracket
Attempt to resolve sender address when the MTA handed it as bracketed IP address (e.g.: [192.0.2.18] ). Default is to leave it as is.
maxpeek
Limit (in bytes) how much of messages are examined for header and body searches.
lazyaw
Make auto-whitelist look at just the IP instead of the (sender IP, sender e-mail address, recipient e-mail address) tuple.
domainexact
match on subdomain boundaries instead of the default suffix matching. E.g. if domainexact is not enabled (the default) then gle.com will match google.com in addition to gle.com. If domainexact is enabled then, domain names will match on subdomain boundaries (e.g. gle.com will match mail.gle.com and gle.com but not google.com)
drac db

Tell where the DRAC DB file is. This is only available if DRAC support was compiled in. Here is an example:

drac db "/usr/local/etc/drac.db"

nodrac
Disable DRAC.
logexpired
This option causes greylist entries that expire to be logged via syslog. This allows you to easily collect the IP addresses and sender names and use them for blacklisting, SPAM scoring, etc. Normally, expiration's are only logged if the debug option is set, but that generates a lot of extra messages.
localaddr
This keyword can be used to manually define the local MTA's IP address for such uses as spf self and p0f in absence of the milter-API {if_addr} macro support in your MTA (Postfix, Sun/Oracle CommSuite Messaging Server). This is not so useful when using Sendmail, since it serves the macro and the local address can be detected automatically.

The configuration file is reloaded automatically once it is modified when new e-mail arrives. Most configuration keywords will take effect immediately, except the following, which will only take effect after a restart of milter-greylist(8): nodetach, pidfile, socket, and user.

The dumpfreq option can be changed dynamically, but the change will only take effect after the next dump.

multiracl
By default, once a RCPT-stage ACL whitelists a recipient, next recipient gets automatically whitelisted. This historical behavior can be considered a bug, and this option disables it.

Format Strings

Various statements in the configuration file accept format strings, where the following % prefixed tokens are substituted. Here is the complete list of available substitutions (Note that some substitutions are not relevant in any context).

%r
the message recipient e-mail address. This is not substituted for DATA stage ACL since there can be multiple recipients for the message.
%f
the message sender e-mail address
%i
the sender machine IP address
%j
the reversed sender machine IP address. For instance, 192.0.2.12 becomes 12.2.0.192.
%I
the sender machine IP address masked by a CIDR. Example: %I{/24}
%d
the sender machine DNS address
%h
the SMTP transaction HELO string
%mr
the mailbox part of %r (before the @ sign). This is not substituted for DATA stage ACL since there can be multiple recipients for the message.
%sr
the site part of %r (after the @ sign). This is not substituted for DATA stage ACL since there can be multiple recipients for the message.
%mf
the mailbox part of %f (before the @ sign)
%sf
the site part of %f (after the @ sign)
%md
the machine part of %d (before the first . sign)
%sd
the site part of %d (after the first . sign)
%Xc
the SMTP code returned
%Xe
the SMTP extended code returned
%Xm
the SMTP message returned
%Xh
the message displayed in the X-Greylist header
%D
Comma-separated list of Dnsrbl for which the sender host matched
%M
a sendmail macro value. Examples: %Mj or %M{if_addr}
%g
a regex back reference. For instance, %g{\2} is substituted by the string matching the second parenthesis group in all ACL regex clauses
%T
a brace-enclosed strftime(3) format string that will be substituted by the system time. Example: %T{%Y%m%d:%H%M%S}
%v
milter-greylist's version
%G
Offset to GMT (e.g.: -0100)
%C
Sender IP country code, as reported by GeoIP. This is only available if milter-greylist was built with GeoIP support
%Fx
p0f OS fingerprint genre and detail. This is only available if milter-greylist was built with p0f support.
%V
Shortcut to "milter-greylist-%v (%Mj [%M{if_addr}]); %T{%a, %d %b %Y %T} %G (%T{%Z})"
%S
the action performed: accept, tempfail, or reject.
%A
the line number of the ACL that caused the action.
%a
the id string of the ACL that caused the action. If no id was given, the line number is used instead.
%cA
the line number of the ACL being evaluated, whether it matches or not.
%ca
the id string of the ACL being avaluated, whether it matches or not. If no id was given, the line number is used instead.
%Et
total elapsed time in seconds before a greylisted message has been accepted
%Eh
hours elapsed
%Em
minutes elapsed (modulo one hour)
%Es
seconds elapsed (modulo one minute)
%E
shortcut to %Eh:%Em:Es
%Rt
total remaining time in seconds before a greylisted message will be accepted
%Rh
hours remaining
%Rm
minutes remaining (modulo one hour)
%Rs
seconds remaining (modulo one minute)
%R
shortcut to %Rh:%Rm:Rs
%Hs
SpamAssassin score (if build with SpamAssassin support)
%pn
Name of last LDAP or CURL gathered property that matched an ACL.
%pv
Value of last LDAP or CURL gathered property that matched an ACL.
%pr
Recipient that caused storage of the last matching LDAP or CURL gathered property. %P a LDAP or CURL gathered propery. Example: %P{mail} Note that this copes very badly with multivalued properties.
%Qd
DKIM query result (pass, fail, etc.), if built with DKIM support.
%Qs
SPF query result (pass, (soft)fail, etc.), if built with SPF support.
%QA
Authentication results summary, suitable for Authentication-Results header. Will included formatted query results from DKIM and SPF if checked.
%QS
SPF result, suitable for Received-SPF header. Available when compiled with libspf2.
%%
a single % character

Authors

Emmanuel Dreyfus <manu@netbsd.org>

milter-greylist received many contributions from (in alphabetical order): Adrian Dabrowski, Aida Shinra, Adam Katz, Alexander Lobodzinski, Alexandre Cherif, Alexey Popov, Andrew McGill, Attila Bruncsak, Benoit Branciard, Bernhard Schneider, Bob Smith, Constantine A. Murenin, Chris Bennett, Christian Pelissier, Cyril Guibourg, Dan Hollis, David Binderman, Denis Solovyov, Elrond, Enrico Scholz, Eugene Crosser, Fabien Tassin, Fredrik Pettai, Gary Aitken, Georg Horn, Gert Doering, Greg Troxel, Guido Kerkewitz, Hajimu Umemoto, Hideki ONO, Ivan F. Martinez, Jacques Beigbeder, Jean Benoit, Jean-Jacques Puig, Jeff Rife, Jim Klimov, Jobst Schmalenbach, Joe Pruett, Joel Bertrand, Johann E. Klasek, Johann Klasek, John Thiltges, John Wood, Jorgen Lundman, Kazuyuki Yoshida, Klas Heggemann, Kouhei Sutou, Laurence Moindrot, Lev Walkin, Manuel Badzong, Mart Pirita, Martin Paul, Matt Kettler, Mattheu Herrb, Matthias Scheler, Matthieu Herrb, Michael Fromme, Moritz Both, Nerijus Baliunas, Ole Hansen, Pavel Cahyna, Pascal Lalonde, Per Holm, Petar Bogdanovic, Petr Kristof, Piotr Wadas, R P Herrold, Ralf S. Engelschall, Ranko Zivojnovic, Remy Card, Rick Adams, Rogier Maas, Romain Kang, Rudy Eschauzier, Stephane Lentz, Steven Hiscocks, Thomas Scheunemann, Tim Mooney, Vincent Dufresne, Wolfgang Solfrank, and Yaroslav Boychuk.

Thanks to Helmut Messerer and Thomas Pfau for their feedback on the first releases of this software.

See Also

milter-greylist(8), sendmail(8), syslogd(8).

Evan Harris's paper:
http://projects.puremagic.com/greylisti…
milter-greylist's web site:
http://hcpnet.free.fr/milter-greylist/

Referenced By

milter-greylist(8).

May 10, 2005