submission configuration issues

[Jean-Daniel Dupas]

Hello,

I'm having trouble configuring the submission proxy.

I have configured the submission service as follow:

submission_host = smtp.example.com
submission_relay_host = localhost
submission_relay_port = 8587
submission_relay_rawlog_dir = /var/log/dovecot/
submission_relay_trusted = yes

My main issue is that until I login, dovecot-submission won't connect to the backend and query the capabilities and so won't report the right capabilities.

That mean that the first EHLO message don't get the right capabilities list.

"
EHLO example.com

250-smtp.example.com
250-8BITMIME
250-AUTH PLAIN LOGIN
250-BURL imap
250-CHUNKING
250-ENHANCEDSTATUSCODES
250-SIZE
250 PIPELINING
"

This list don't contains VRFY, DNS, and SIZE is not specified (all of these is present in backend EHLO response).
After login, if I send an new EHLO command, everything is properly reported. The raw log shows that unlike what the documentation says, 
dovecot don't try to connect to the backend until the user is properly logged.

In my raw log I show that after I logged in dovecot-submission, the later open a connection to the backend and send a X-CLIENT command.


Now, if I try to force the capabilities by using:

submission_backend_capabilities = VRFY 8BITMIME DSN

dovecot properly reports all SMTP capabilities in the first EHLO response, but it completely stops emitting X-CLIENT command to the backend 
and try to simply forward the command without authentication, which result in postfix rejecting the command with an unauthorized user error.

What is wrong with my configuration ?
Thanks.

Jean-Daniel