Enhancement Request -- Improve Error Message: "server does not support authentication"

[rino1]

Summary

The current msmtp error message:

server does not support authentication

can be misleading in certain configurations.

Context

In scenarios where: - auth on is enabled - The SMTP server advertises
AUTH only after STARTTLS - TLS is disabled or misconfigured on the
client side

msmtp reports that the server does not support authentication.

However, the server may fully support authentication. The issue can
originate from client-side TLS configuration preventing the server from
advertising the AUTH capability.

Problem

The current error message does not distinguish between:

1. A server that genuinely does not support SMTP AUTH
2. A server that withholds AUTH until after STARTTLS
3. A client-side TLS misconfiguration preventing AUTH advertisement

This can mislead users into diagnosing a server-side issue when the root
cause is client-side configuration.

Proposed Improvement

Replace the current message with something more precise, for example:

AUTH capability not advertised by server.
This may be caused by missing STARTTLS or TLS configuration issues.

or:

Server did not advertise AUTH.
Please verify TLS/STARTTLS configuration.

Expected Benefit

• Reduced troubleshooting time
• Clearer separation between protocol-level capability and
  session-level advertisement
• Improved diagnostic clarity

This is not a functional bug, but a usability/diagnostic enhancement
request.

[rino1]

no interest in my proposal?