Process more emails concurrently

WARNING: Processing more concurrent emails require more RAM.

Amavisd-new is content filter, it invokes SpamAssassin and ClamAV for spam/virus scanning, it also offers additional features like DKIM signing and verification.

In Amavisd config file, $max_servers sets the number of concurrent Amavisd processes and it must match the number set in /etc/postfix/ maxproc column for the smtp-amavis service. Sample settings:

# File: /etc/amavisd/amavisd.conf

$max_servers = 4;
# File: /etc/postfix/

smtp-amavis unix -  -   -   -   4  smtp

Both values should be identical for two reasons: If Amavisd offers more processes than Postfix will ever use, Amavisd wastes resources. On the other hand, if Postfix starts more dedicated transports than amavisd can handle simultaneously, e-mail transport will be refused and logged as error.

If many emails stalled in mail queue (check with command postqueue -p), and your server has powerful CPU and memory, you can increase the number of concurrent Amavisd processes, so that it can process more emails at the same time. Sample setting:

# File: /etc/amavisd/amavisd.conf

$max_servers = 10;

Restarting Amavisd service is required.

# File: /etc/postfix/

smtp-amavis unix -  -   -   -   10  smtp

Note: If you don't want to modify /etc/postfix/, it's ok to set smtp-amavis_destination_concurrency_limit = 10 in /etc/postfix/ instead.

Restarting Postfix service is required if you modified /etc/postfix/, reloading OR restarting is required if you modified /etc/postfix/