To configure MIMEDefang, you have to edit the file /etc/mail/mimedefang-filter. This is a Perl source file, so you have to know Perl. Go ahead and read the man pages mimedefang(8), mimedefang.pl(8) and mimedefang-filter(5). There are some sample filters in the /usr/share/doc/mimedefang-* directory. In order to complete the installation of MIMEDefang, you will need to add for example the following lines to your /etc/mail/sendmail.mc file (which requires, in turn, the installation of sendmail-cf package): define(`MILTER', `1')dnl define(`confMILTER_LOG_LEVEL', `6')dnl INPUT_MAIL_FILTER(`mimedefang', `S=unix:/var/spool/MIMEDefang/mimedefang.sock, F=T, T=S:1m;R:1m;E:5m')dnl Use "systemctl restart sendmail.service" to rebuild your /etc/mail/sendmail.cf file, run "systemctl enable mimedefang.service" to start MIMEDefang during boot time per default and execute "systemctl enable mimedefang.service" to start the service. When everything was correct, MIMEDefang should now do its job... For the integration of MIMEDefang and ClamAV, some manual steps are required: (1) Add the user clam to the defang group after installing MIMEDefang usermod -a -G defang clam (2) Find and modify the following lines in /etc/clamd.conf: LocalSocketGroup defang LocalSocketMode 660 and optionally disable the TCP listener if you are only using the UNIX socket from MIMEDefang (below): #TCPSocket 3310 #TCPAddr 127.0.0.1 (3) Enable MD_ALLOW_GROUP_ACCESS=yes in /etc/sysconfig/mimedefang (4) Configure /etc/mail/mimedefang-filter to use clamd via UNIX socket: $Features{'Virus:CLAMD'} = 1; $ClamdSock = '/var/run/clamav/clamd.sock'; (5) Restart the MIMEDefang and clamd services (clamd first).