socket bind() to port 25 for address (any IPv4) failed: Address already in use
If you get this error message:
socket bind() to port 25 for address (any IPv4) failed: Address already in use: waiting 30s before trying again (6 more tries) ….
That means there is already a smtp program listening on Port 25. Port 25 is reserved for Exim. To find out what other application(s) is listening to Port 25, SSH to the server and run the following command:
/bin/netstat -lnp | grep 25
You can either stop or kill the application that is listening to Port 25. Then restart Exim running the following command:
/sbin/service exim restart