iRedAPD-2.6 implements SRS (Sender Rewriting Scheme) support, and switches
to syslog for logging. To enable SRS support, please follow this tutorial:
https://docs.iredmail.org/srs.html
It's recommended to upgrade them when you have time, if you deployed iRedMail
server with our iRedMail Easy platform[1], please login to iRedMail Easy[2] and
upgrade the server with few clicks.