Restart Postfix Using systemd Without Dropping Connections

SuperDuperApps asked:

On CentOS7, using systemd or otherwise, is there a better way to restart postfix than:

sudo systemctl restart postfix

Won’t the above break any active mail connections that are happening? I’m looking for something like Apache’s graceful restart and wondering if it’s possible, or if it’s necessary.

My answer:

Very few changes to postfix configuration require a full restart. It’s almost always sufficient to have postfix reload its configuration while still running.

systemctl reload postfix

Even the man page mentions this.

              Note: in order to refresh the Postfix mail system after  a  con-
              figuration  change,  do  not  use the start and stop commands in
              succession. Use the reload command instead.

And even if mail connections do break, when you have to restart the mail server, the sending mail server will just try again later.

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