All of a sudden, mail function stopped working on my server.
After investigating the logs, I found the following entry:
amavisd-new: Fails to responde to connection to port 10024
I also found messages like this one:
ClamAV-clamd av-scanner FAILED: run_av error: Too many retries to talk to /var/run/clamav/clamd.ctl
Problem was not related to postfix server, but rather to the antivirus|antispam amavis deamon.
The solution, once you know it, is pretty simple. It consists in restarting amavis & clamav daemon so that connection to port 10024 will be answered again. Just in case, we will restart clamav-freshclam as well (only one of the two is required, I don’t remember exactly which one know)
Simply run as root:
/etc/init.d/amavis restart /etc/init.d/clamav-daemon restart /etc/init.d/clamav-freshclam restart
Note: normally all messages for which sending failed have been queued and will be automatically sent as soon as port 10024 (ie. clamav|amavis daemons) are restarted => no information is lost, it has only been delayed (great news!)