Bug#312575:

[Geoff Denning]

I've discovered both the cause and workaround for this problem, as I encountered the same bug myself this morning.

The debian package elegantly creates a /etc/mail/m4/clamav-milter.m4 configuration file that contains the INPUT_MAIL_FILTER specifying the location of the milter socket file.  The location of the socket file is correct, and actually does correspond to the file configured in /etc/init.d/clamav-milter.  However, when clamav-milter checks for the INPUT_MAIL_FILTER directive in sendmail, it only checks sendmail.mc, and ignores all the included configuration files in the m4 directory.  The workaround is to move the INPUT_MAIL_FILTER directive from the /etc/mail/m4/clamav-milter.m4 file to the /etc/mail/sendmail.cf file (and delete the /etc/mail/m4/clamav-milter.m4 file).  Technically, this should probably be considered a clamav-milter bug, but for now, the package should probably add the INPUT_MAIL_FILTER directive to the sendmail.cf file.