I don’t think Fail2ban will stop an account from sending spam mail. The tool @stefan1959 sugested, Diagnostics, will tell you if your email address is an open relay and other useful things about it.
Turning on Fail2ban [recidive] jail with reduced matches and increased jail times is a good idea.
I add file /var/log/fail2ban.log to System Logs Viewer for convenience. If I see a few Found IPs from the same subnet I look it up and if it is from a country I don’t want or need traffic from I set a permanent larger subnet drop rule in FirewallID. It keeps the chatter down.
When you restart and go to view the fail2ban.log you see a list of all the banned IPs in numerical order re-establishing the ban if you find that useful.
Some info here:
Are the default Fail2ban settings enough what are the reccomendations