OpenBSD Journal

E-Mail Content Filtering with OpenBSD - An Update

Contributed by jose on from the safer-mail dept.

Marc Balmer writes =: "On October 16, I first presented a new software to kill E-Mail viruses on OpenBSD (and other Unixes): smtp-vilter.

smtp-vilter, which is developed and maintained on OpenBSD, has since evolved and seen enhancements both securitywise and featurewise. It can now be run as non-root user in a chroot jail and besides scanning for e-mail viruses it can be used to scan for spam as well.

smtp-vilter decides whether to pass, discard or simply mark an e-mail message based on the results of a content scan and user defined strategies.

smtp-vilter does not do the scanning by itself, it relies on third-party products like ClamAV (free), Symantec Antivirus (commercial) or SpamAssassin (free) for this purpose. smtp-vilter uses the milter API to communicate with sendmail and one or more backends to communicate with the actual virus or spam scanning engines. The backends can be chained to perform a series of checks on one message in one run.

The software is highly configurable and provides mechanisms for secure operation.

The backends included in the distribution provide support for the Clam AntiVirus Daemon (clamd), the Symantec Anti Virus Scan Engine (savse), and SpamAssassins Daemon (spamd). The backends are realised as shared libraries that are loaded dynamically when smtp-vilter starts. All backends have their own configuration file.

We currently use it to scan an average 100'000 E-Mails per day.

smtp-vilter can be downloaded at "

(Comments are closed)

  1. By pepper () on

    All very exciting but its still to do with sendmail.

    Why OpenBSD doesnt come with an MTA like postfix ( like NetBSD has ) again?

    1. By Anonymous Coward () on

      OpenBSD does come with procmail-- it's in the ports collection.

    2. By schubert () on

      postfix is in ports if you want it but like qmail, there are license issues. The postfix license is not "free" enough (IBM Public License) to replace sendmail

  2. By Joe Price () on

    Sendmail IS the default mail service for obsd. If it was a problem I believe they would either bypass the BSD >= license for system software (gcc?).

    Everyone seems to always dog sendmail. I like it. I've been using it for about 6 years for personal use, and for approx. 20 domains over the years. With spam and things these days I'm sure it see's enough traffic. I use access.db to block certain people, I use virtusertable for virtual hosts. Not too crazy. The only thing I plan on implementing is crm114 spam checking, hopefully using vilter :)

    Now I'm never actually used any of the other email servers like postfix, or qmail - so I assume I am biased. I think it's important for users (especially new) to see articles both pro and con articles for software. All software has them.

    I admin at first sendmail appears somewhat cryptic. =/

    1. By Will Boyce () on

      I've tried most, and I liked qmail.. Its easy to use, bit of a ball-ache to get installed etc, but works nice, does the job, and doesn't overly confused with stupidly complex configuration files, ala sendmail ;)..

      Give it a try, bet you'll be converted ;). I use qmail on all my servers, although admittedly my openbsd box I use for everyday use still has sendmail, cos I just cba messing about with qmail.. If only it could be in ports, damn weird license. :/

  3. By Paul Pruett () on

    I have had some problems with clamav-milter and clamd. Before 0.65, sometimes clamav-milter would stop, and with 0.65 stable after about 5 days clamav-milter would time out like clamd was not responding or other....

    I look forward to trying clamav with smtp-vilter to see if it performs better than the clamav-milter that is contributed with clamav.

    1. By zenz () on

      I just want to know how to config the clamd and smtp-vilter to check the archives, It seems that the smtp-vilter will passthrough archives in email.

  4. By Anonymous Coward () on

    .. for email/content filtering. Thats cool. I actually wish I heard about this sooner (my bad for not keeping up @, so I could have evaluated it at the same time I evaluated MailScanner combo'd /w ClamD. Likely these two together take up more resources than other options, but it matters not when you have a small number of email accounts to look after and a decent i386 workstation turned simple server can handle it.


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