Issue Description
I created a simple alias for my admin user [email protected] with the following settings:
Local part: postmaster
Domain: test.com
Enabled: true
Sending an e-mail to [email protected] results in an error e-mail Mail Delivery System - Undelivered Mail Rturned to Sender. Within the e-mail it states that the user [email protected] does not exist.
Expected Behavior
E-Mail should be delivered to [email protected]
Actual Behavior
E-Mail is not being delivered
Reproduction Steps
Create an alias as described above.
Relevant Log Output
Debug log doesn’t show anyhing related to this non deliverable -email
Stalwart Version
v0.16.x
Installation Method
Docker
Database Backend
SQLite
Blob Storage
SQLite
Search Engine
Internal
Directory Backend
Internal
I have reviewed the documentation and FAQ and confirm that my issue is NOT addressed there.
on
I have searched this support forum (open and closed topics) and confirm this is not a duplicate.
on
I understand that topics in this category are triaged by a bot first but a human reply will follow up. If I’d prefer a human-only reply, I’ll add the no-ai tag to my topic.
on
There isn’t a dedicated docs page for alias configuration that I can ground a detailed answer in, so I’ll note what’s observable from your description and flag it for a human follow-up.
A few things worth double-checking in the meantime:
-
postmaster is a reserved address. RFC 5321 requires every domain to accept mail for postmaster, and Stalwart may handle this address internally before consulting user-defined aliases. It’s worth testing with a non-reserved local part (e.g. [email protected]) to confirm whether the alias mechanism itself works correctly or whether the issue is specific to postmaster.
-
Alias target format. Confirm that the alias destination is set to the full address [email protected], not just admin.
-
Delivery vs. alias lookup. The fact that the debug log shows nothing related to the failed delivery is unusual and may indicate the message is being rejected at a stage before alias resolution. Check your SMTP logs (not just debug) for any 550/551 rejection lines around the time of the test send.
A human community member or Stalwart staff member will follow up with more authoritative guidance on the postmaster reservation question.
This is an automated reply from the Stalwart Help Bot. Other community members may follow up if this answer is incomplete or wrong. If you found it useful, mention @helpbot in any reply to ask follow-up questions and the bot will respond again.
Also ran the test with another alias [email protected] and it did not work either.
Just to make sure, sending and receiving from an to [email protected] works without any issues.
Please try setting the log level to trace, send a test email and check what the logs report.