MailScanner is a very powerful daemon that can do several checks for viruses and spam on emails. While it uses an external Scanner for the virus checks (e.g. Sophos, FPProt or ClamAV), SpamAssassin is used for doing the Spam checks. All this can be done with exim, too - and already at SMTP time, which offers the possibility to use the results (Spam or Non-Spam, Virus found or not) to decide if the mail is to be rejected or accepted.

But MailScanner can do a little more: It can also "disarm" harmful content of HTML mails. It can even convert HTML mails to PlainText mails - depending on the configuration. Thus, MailScanner offers a bit more flexibility, but there are also some disadvantages in comparison with exim: - SpamAssassin_ cannot be run in daemon mode (as "spamd") - At the time a mail is being processed, the MTA has already accepted it - whether it's spam/virus or not. But (from the author's point of view) you get most flexibility when combining exim's and MailScanner's features: Let exim, spamd and your virus scanner decide if the mail is accepted and then pass it through MailScanner to disarm potentially harmful HTML Code.

The setup is a bit tricky: You need two exim daemons. One of them (the "listener") does accept (or reject |;-)| mails arriving via SMTP. Whenever it accepts an email, it is put in MailScanner's "Incoming Queue". MailScanner then runs its checks on this email and finally invokes the second exim daemon which is only responsible for deliveries.

The setup procedure is described in the MailScanner docs. MailScanner has been written in Perl and comes with an installer that builds and installs all necessary Perl modules.

See also: `MailScanner Home Page`_

Christian Schmidt <christian(at)siebenbergen.de>