No auth mechanism available with Mail relay rule

[DavidePrincipi]

The SMTP AUTH LOGIN authentication method is not considered valid by the Mail SMTP client. Some SMTP servers (e.g. Outlook.com) do not provide the PLAIN method and our client does not support LOGIN as it used to do in NS7: the SMTP authentication fails with a no mechanism available error message.

Steps to reproduce

• Add a custom configuration directive for Postfix smtpd service: smtpd_sasl_mechanism_filter = login. This actually disables the PLAIN method.
• Configure a "fake" relay rule:
  • destination: administrator@fake.test
  • hostname: 10.5.4.1 (Mail itself)
  • port: 10587 unencrypted local-only
  • authentication: ENABLED, set credentials of a valid Mail user
  • TLS: DISABLED, not needed for this test
• Save the rule
• Send a test message: connect to port 587 or 465 with your MUA (Thunderbird?) and send a message to administrator@fake.test
• Go to the Mail Queue page

Expected behavior

Apart from the fake.test domain which is an undeliverable domain, the message should be delivered after a succesful SMTP authentication. The Mail log evidence should be something like

2024-05-17T13:23:38+02:00 [1:mail3:postfix/smtpd] 581C96C756475: client=cluster-localnode[10.5.4.1], sasl_method=LOGIN, sasl_username=davidep2

Actual behavior

The message is in the queue. If you see the message delay reason is

SASL authentication failed; cannot authenticate to server 10.5.4.1[10.5.4.1]: no mechanism available

It seems Postfix does not support LOGIN method: maybe the container is missing some Cyrus library?

Components

Mail 1.4.0

See also

https://community.nethserver.org/t/relay-implementation-does-not-work-on-smtp-outlook/23659

---

Thanks to france

[stephdl]

QA

Test the bug is not reproducible (as alternative you have another way to validate the code is workable, you need an account to outlook.com)

• create or update a mailserver with ghcr.io/nethserver/mail:1.4.1-dev.1

[stephdl]

verification seems good at https://community.nethserver.org/t/relay-implementation-does-not-work-on-smtp-outlook/23659/12

[DavidePrincipi]

Released https://github.com/NethServer/ns8-mail/releases/tag/1.4.1