SMC anti-spam e-mail filter

SMC anti-spam e-mail milter (plug-in) is an software application designed to significantly reduce the amount of SPAM/UCE (junk-mail) you receive. SMC uses a greylisting like technique to stops the junk-mail and a set of dynamic auto "whitelists" for unknown, but legitimate senders. [PAD 2.0]


2008-06-30: Version 2.1 released. Added classic SPF support (file spf.c), add 'classicspf' option in config file (enabled by default). Fixed potencial bug in cache algorithm. Configuration reload added on signal 1 (SIGHUP). Updated FreeBSD startup script (file "NS Relay" algorithm renamed to AutoSPF. Auto-confirmation algorithm renamed to AutoSWL (Auto Sender White List). AutoSPF algorithm optimization. Small bug fix in AutoSPF code. Add new 'autospf' and 'autoswl' options in config file. Bug fix in greylisting code. Minor changes to config defaults. Check return codes, various potential bugs fixed. {client_addr} and {client_name} macros are no longer required. Added 'pidfile' parameter in config file to define the new pid file location if required. Added 'database' parameter in config file to change the default location of filter database file location. Code cleanup and optimization. Documentation fix.


For more downloads and previous releases of the SMC filter please visit our project page:

Additional Downloads

For more information about libspf2 please visit the project page:

SMC Algorithms

SMC uses 3 original algorithms, one of which is AutoSPF (Check relay by NS) simulates a dynamic whitelist and will always accept the messages from mail systems satisfying to following conditions:
  1. Mail domain name (the host part of the sender's e-mail address) must have an MX records;
  2. Mail domain name and the connection host address must be resolved;
  3. Connection host must be listed at the one of nameservers which hold the sender's mail domain name.
The second from the developed algorithms is a greylisting like algorithm or "check delays" which is based on statistical check of delivery delays, generated by a [tempfail] return code, that allows to exclude a direct receiving of a mail, which not passed through the standard mail server.
NOTE: Using this feature the delivery of the mail from unknown, but legitimate senders will be delayed for a count of 5-minutes checks, which setted by the "maxcount" configuration parameter.
And the third of original algorithms is AutoSWL (Auto Sender White List) or "auto-confirmation" algorithm: The sender of a "mail contact" (sender-recipient pair) means as authenticated (whitelisted) if the filters statistics module has registered the both of a sended forward (request) and a received backward (reply) messages of this contact. The messages from the such authenticated senders will never be delayed by the previous greylisting algorithm.

SMC Headers

SMC will tag the incoming messages with the next set of traditional and widely used headers:
X-Spam-Report: System report which explains the reason of a Spam-Flag value apropriation.
X-Spam-Checker-Version: SMC-milter [Program Version]
X-Virus-Scanned: Name of virus scanner if enabled
For example:
X-Spam-Flag: NO
X-Spam-Report: Host is related to
X-Spam-Checker-Version: SMC-milter 2.0
X-Virus-Scanned: ClamAV using SMC-milter


Alexander Djourik <>
Stanislav Ivankin <>
Pavel Zhilin <>
RHEL/CentOS/Mandriva/Fedora packages are made by Denis Frolov <>