Look at ISPConfig.

It isn’t simple but has all of the services you require:

postfix (SMTP)

dovecot (IMAP)

LMTP

MySQL databases for management

Web-based management interface

I used to have a portable hotspot named “NSA surveillance van 17”

I’ve commented to my cow-orkers that “Typescript is the bag they put over Javascript’s face so you don’t have to look at it anymore.”