[gX:/etc/mail] # pkg_add -r procmail

[gX:/etc/mail] # cat gX.class.mc
OSTYPE(freebsd6)
FEATURE(local_procmail)
FEATURE(`use_cw_file')
FEATURE(access_db, `hash -o -T<TMPF> /etc/mail/access')
FEATURE(virtusertable, `hash -o /etc/mail/virtusertable')
MAILER(local)
MAILER(smtp)
MAILER(procmail)

[gX:/etc/mail] # make cf
[gX:/etc/mail] # make install
[gX:/etc/mail] # /etc/rc.d/sendmail restart

root@gX:~# apt-get install procmail

root@gX:~# rcsdiff /etc/postfix/main.cf
43a44
> mailbox_command = /usr/bin/procmail -d "$USER"

root@gX:~# /etc/init.d/postfix force-reload

http://www.freebsd.org/doc/ru/books/handbook/mail-procmail.html

gX# cat ~mailuser/.procmailrc
:0c
backup_mail

gX# cat ~mailuser/.procmailrc
:0
* multipart
{
  VIRUS=`/usr/bin/clamdscan --mbox --disable-summary --stdout -`

  :0 Di
  * VIRUS ?? FOUND
  /dev/null
}

gX# cat ~mailuser/.procmailrc
:0
* ^To.*ivanov\@specialist\.ru.*
! ivanov

:0 ^To.*petrov\@specialist\.ru.*
! petrov