Hi @greavette
Mail server definition:
https;//ip-address:9090 → Applications → Email → Settings → Domains
The domain should appear, otherwise Create a new domain.
DKIM not really necessary but recommended
User:
https;//ip-address:9090 → System → Users & Groups
If module Webmail is installed, to check email: https://ip-address/webmail/
Hoping it will help you.
Michel-André