submission configuration issues

Jean-Daniel jddupas at
Sun Jul 28 00:17:42 EEST 2019

> Le 27 juil. 2019 à 23:13, Stephan Bosch <stephan at> a écrit :
> On 23/07/2019 17:13, Jean-Daniel Dupas via dovecot wrote:
>> Hello,
>> I'm having trouble configuring the submission proxy.
>> I have configured the submission service as follow:
>> submission_host =
>> 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 is true and expected. No connection to the relay server is made until the user is logged in.
>> That mean that the first EHLO message don't get the right capabilities list.
>> "
>> 250-8BITMIME
>> 250-BURL imap
>> 250-SIZE
>> "
>> 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.
> Oh, then we need to adjust the documentation. This is normal behavior.

This is in the default 20-submission.conf file:

# By default, the submission service first connects to the relay server to
# determine the support for such capabilities before sending the initial EHLO
# reply to the client. If the list of capabilities returned by the relay server
# is somehow unreliable or it is undesirable to start the connection to the
# relay server before the first mail transaction is started, the backend
# capabilities can be configured explicitly using the
# submission_backend_capabilities setting.
#submission_backend_capabilities =

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