<snip/>
"Your DH parameters are too weak. You should generate at least 2048 byte parameters."
To be honest, I don't even recall setting up DH parameters. I would guess that probably happened when I was setting up ssl?
openssl gendh 4096 > /path/to/dh.pem
Alternatively, update to latest dovecot from https://repo.dovecot.org and disable DH support completely. See https://doc.dovecot.org/installation_guide/upgrading/from-2.2-to-2.3/#diffie...
Again, thank you to each of you for helping with this. I really try not to send stuff like this to mailing lists that are technical in nature, but this is important business mail he's potentially missing and I'm a bit out of my league. First project once this gets fixed will be learning how to back up the server.
Christy
Aki