routinely I'm seeing lots of login attempts to my mail server trying out various login names starting from A to Z coming from the one IP on one day and another IP on another day. Is there any means to detect this type of activities and block accordingly? I asked Watchguard and it appears they don't support this on their XTM series. Anything else I can do other than to have a super long password?
This is a typical example of the "background noise" you'll find on most servers exposed to the internet.
A common solution is to have a script parse your log files to find those repeat offenders and then block the originating ip-adresses in the servers local firewall.