SMC anti-spam milter is a software that dramatically decreases the quantity of unwanted emails such as SPAM/UCE.
In addition, this software comes with a set of useful features that help preserve the recipients' mail from dangerous message attachments, HTML includes, and other harmful content. SMC is a Sendmail milter (plugin) that can block junk-mail without receiving it.
One of the three original algorithms used by SMC is the "Check relay by NS" which simulates a dynamic whitelist and will always accept messages from mail systems satisfying the following conditions: 1. Mail domain name must have an MX record, 2. Mail domain name and the connection host address must be resolved, and 3. Connection host must be listed at one of the nameservers that hold the sender's mail domain name.
The second algorithm, "check delays," operates through statistical checks of delivery delays generated by a [tempfail] return code, which allows excluding receiving any mail that has not passed through the standard mail server. When using this feature, delivery of mail from unknown but legitimate senders may be delayed for up to 10 minutes checks, which is set by the "maxcount" configuration parameter.
The third algorithm, "auto-authentication," authenticates (whitelists) the sender of a "mail contact" (sender-recipient pair) if the filters statistics module has registered both a sent forward (request) and a received backward (reply) messages of this contact. Messages from authenticated senders will never be delayed by the previous "check delay" algorithm.
The latest release of SMC anti-spam milter now includes classic SPF support and configuration reload has been added on signal 1 (SIGHUP). The "NS Relay" algorithm is now called AutoSPF, and the auto-confirmation algorithm has been renamed to AutoSWL (Auto Sender White List). Additionally, there is a small bugfix in the AutoSPF and data caching code, new options in the config file, and minor changes to config defaults. The code has been cleaned up and optimized, and there are documentation fixes.
Overall, SMC anti-spam milter is a great software that seamlessly filters out junk-mail, drastically minimizing the risk of spam and protecting recipients' mailboxes.
Version 2.1: N/A