Submission service and SMTP AUTH capability

[Germán Herrera]

Hi Everyone!

I've setup dovecot 2.3.2.1 on a Gentoo server. I want to configure the 
submission service in order to replace the corresponding part in Postfix 
(which is my SMTP server).
I configured submission it with just a few options different of the 
default ones:

submission_client_workarounds = whitespace-before-path
submission_relay_host = 127.0.0.1
submission_relay_port = 10026
submission_relay_trusted = yes

The issue I'm having is that the SMTP AUTH is enforced and performed 
correctly, but it doesn't get published on the server capaabilities when 
the connection doesn't come from localhost. This causes issues with some 
smtp clients which authenticate (python smtpclient).

When I telnet the submission service from localhost I get:

220 (protected hostname) Dovecot ready.
EHLO L
250-(protected hostname)
250-8BITMIME
250-AUTH PLAIN LOGIN
250-BURL imap
250-CHUNKING
250-ENHANCEDSTATUSCODES
250-SIZE
250-STARTTLS
250 PIPELINING
quit
221 2.0.0 Bye

But when I do the same from another host other than the one running 
dovecot (telnetting the submission port):

220 (protected hostname) Dovecot ready.
EHLO L
250-(protected hostname)
250-8BITMIME
250-BURL imap
250-CHUNKING
250-ENHANCEDSTATUSCODES
250-SIZE
250-STARTTLS
250 PIPELINING
quit
221 2.0.0 Bye

As you can see, the AUTH capability is not there.
Do you know what could be causing this issue? Your help is much 
appreciated!
German