New Dovecot service: SMTP Submission (RFC6409)

[Robert Schetterer]

Am 12.12.2017 um 00:14 schrieb Stephan Bosch:
> Hi,
> 
> As some of you know, I started implementing the SMTP submission proxy a
> few years ago. It acts as a front-end for any MTA, adding the necessary
> functionality for an SMTP submission service, also known as a Mail
> Submission Agent (MSA) (https://tools.ietf.org/html/rfc6409). The main
> reason I created this, back then, was implementing the BURL capability
> (https://tools.ietf.org/html/rfc4468). The main application of that
> capability -- together with IMAP URLAUTH -- is avoiding a duplicate
> upload of submitted e-mail messages; normally the message is both sent
> through SMTP and uploaded to the "Sent" folder through IMAP. Using BURL,
> the client can first upload the message to IMAP and then use BURL to
> make the SMTP server fetch the message from IMAP for submission, thereby
> avoiding a second upload. Apart from BURL, the submission proxy service 
> also adds the required AUTH support, avoiding the need to configure the
> MTA for SASL authentication. More SMTP capabilities like CHUNKING and
> SIZE are supported, without requiring the backend MTA supporting these
> extensions. Other capabilities like DSN currently require support from
> the backend/relay MTA.
> 
> At this point, the submission proxy is still pretty basic. However, it
> will provide a basis for adding all kinds of functionality in the (not
> so distant) future. For the first time, it will be possible to act upon
> message submission, rather than only message retrieval; e.g. plugins can
> be devised that process outgoing messages somehow. Examples of the
> things we could do are adding Sieve filtering support for outgoing
> messages, or implicitly storing submitted messages to the Sent folder.
> Once a plugin API is devised, you can create your own plugins.
> 
> The reason I send this message now, is that this code is finally merged
> into the Dovecot master repository. This means that it is part of the
> upcoming 2.3 release. Now that it is merged, you can install and test it
> from Github if you like. Feedback is of course appreciated. The
> documentation is still pretty sparse, but there is currently not much to
> configure. Just add "submission" to the protocols and configure the
> relay MTA server. The configuration is currently only documented in the
> example configuration in doc/example-config/conf.d/20-submission.conf.
> The submission service is a login service, just like IMAP, POP3 and
> ManageSieve, so clients are required to authenticate. The same
> authentication configuration will also apply to submission, unless
> you're doing protocol-specific things, in which case you may need to
> amend your configuration for the new protocol. BURL support requires a
> working IMAP URLAUTH implementation.
> 
> I've updated the automated Xi Debian package builder to create an
> additional dovecot-submissiond package. So, if you're using the Xi
> packages, you only need to install that package and configure the relay MTA.
> 
> Regards,
> 
> Stephan.
> 
> 
> 
> 
> 

Hi Stephan, this is extreme cool !


Best Regards
MfG Robert Schetterer

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