Sendmail Confirmation System is an Sendmail milter plugin that is designed to reduce the amount of junk email received. SMC uses a dynamic local and DNS based remote "whitelists" (for known/trusted senders), DNS based "blacklists" (for undesired senders), and an original "autoauthentication" system (for unknown, but legitimate senders). In additional SMC has a set of useful features which allows to preserve mail recipients from dangerous message attachments, HTML includes. SMC is an Sendmail tm milter (plugin), which stops the junk mail messages without receiving one.
SMC uses 3 original algorithms, one of which is "Check relay by NS" simulates a dynamical 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 "check delays" algorithm 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 "autoconfirmation" 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 recieved backward (reply) messages of this contact. The messages from the such authenticated senders will never be delayed by the previos "check delay" algorithm.
What's New in This Release:
· Add checks to prevent overwrite all configuration data during install.
· Minor bug fix in ns-relay code.