amavisd-new 2.4.4 review

amavisd-new is a high-performance and reliable interface between mailer (MTA) and one or more content checkers: virus scanners, and/o

License: GPL (GNU General Public License) File size: 866K Developer: Mark Martinec

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amavisd-new is a high-performance and reliable interface between mailer (MTA) and one or more content checkers: virus scanners, and/or Mail::SpamAssassin Perl module. amavisd-new is written in Perl, ensuring high portability, reliability and maintainability. It talks to MTA via (E)SMTP or LMTP protocols, or by using helper programs. No timing gaps exist in the design, which could cause a mail loss.

It is normally positioned at or near a central mailer, not necessarily where users' mailboxes and final delivery takes place. If looking for a per-user and low-message-rate solution to be placed at the final stage of mail delivery (e.g. called from procmail or in place of a local delivery agent), there may be other solutions more appropriate.

When calling of Mail::SpamAssassin (SA) is enabled, it calls SA only once per message regardless of the number of recipients, and tries very hard to correctly honour per-recipient preferences, such as pass/reject, check/nocheck, spam levels, and inserting spam-related mail header fields.

amavisd-new benefits from the use of Perl module Net::Server, which offers a fast pre-forked multichild process control. amavisd-new provides rfc2821-compliant SMTP server, rfc2033-compliant LMTP server, SMTP client, and generates rfc3462/rfc3464-compliant (ex rfc1892/rfc1894) (non-)delivery status notifications.
This makes it suitable for mail anti-virus and/or anti-spam checking on a busy mail gateways that care for reliability and standards compliance.

amavisd-new grew out of amavisd(-snapshot) (which in turn is a daemonized version of amavis-perl), but through three years of development turned into a separate product, hardly resembling its origin. The code is several times the size of its predecessor, yet faster in throughput, richer in features, compliant to standards, includes optional support for spam detection, and makes virus scanning optional and easier to adjust/extend. Compatibility with helper programs from amavisd(-snapshot) is retained.

All modifications since the original amavisd done by Mark Martinec, with contribution of ideas, patches and reports from the amavis-user mailing list community and individuals.

What's New in This Release:
The program now checks for already running daemons when starting.
A setting to allow amavisd-new in a milter setup to coexist with dkim-milter and dk-milter was added.
A new configuration variable allows for selective disabling of header checks.
The SQL data type of a quarantined mail text was changed to avoid it being associated with a character set.
The timer is now restored after decoding of a textual mail part.
The check for all-whitespace header lines was rewritten to avoid slow evaluation of a regular expression.
Double insertion of the SA summary when defanging is now avoided.
Group write access to a socket in a Courier setup is now allowed.