Recommendations for basic localhost mail server, please?

I've just upgraded from 12.3 to 13.1 using Gnome. One thing that is not working is the Dovecot server which I use to pick up mail from localhost only. Dovecot fails to start due to a permissions problem, and there is a bug report registered but no workaround I have found so far.

So I'm looking for a very simple mail server I can have running on my machine so that Evolution can collect mail (very few messages) from localhost only. Any suggestions?