I've extended the implementation of nssmtpd in various ways and updated the documentation:
https://github.com/naviserver-project/nssmtpd
It addresses now different deployment scenarios, such as
- Send application mail through a local or container relay: connect application mail, trace outgoing acceptance
- Receive Internet mail for selected domains and forward aliases: (configure recipient routing, unknown-recipient rejection and relay denial from an untrusted client)
- Let mail clients submit with a separate SMTP login: enable authenticated submission, STARTTLS, successful login and rejection of invalid credentials
- Delay suspicious senders or hold mail for review: configure incoming mail policy, then quarantine, deferral/rejection reasons, retained messages and controlled release (greylist handling)
- Investigate missing mail, TLS failures or policy decisions: follow the delivery evidence, session/transaction details and upstream relay logs
Hope, this helps somebody!
All the best
-g
