High spam volume on treasurer email alias

One of our officers is getting excessive amounts of spam being sent to the treasurer email alias.

The spammers email is often different so blacklisting each one as they arrive may not be the solution.

Is there anyway to determine if all the spam messages are coming from specific IP address where the spammer is always changing the From email address?

I have already asked the officer to perform a deep scan of malware, viruses and rootkits on their computer. The scan yielded no infections on the officers computer.

I am suspecting some bot that is generating high spam traffic to the treasurer email alias from a specific IP address.

Club 8684 - Manotick Toastmasters
Kent Spott - Club Admin

The original IP can be found in the raw internet  email header