Dovecot submission announces CHUNKING but backend Postfix does not support it

[Aki Tuomi]

> On 20 September 2018 at 14:39 Michael Goth <mg at webflow.de> wrote:
> 
> 
> On 09/20/2018 12:56 PM, Robert Schetterer wrote:
> > Am 20.09.2018 um 11:04 schrieb Michael Goth:
> >> Hello,
> >>
> >> I'm setting up Dovecot 2.3.2.1 as a submission proxy to a Postfix 
> >> backend server. Dovecot announces CHUNKING, but the Postfix backend 
> >> does not support (or announce) it.
> >>
> >> HELO from Postfix:
> >>
> >>    220 backend.mydomain.com ESMTP Postfix (Ubuntu)
> >>    ehlo test
> >>    250-backend.mydomain.com
> >>    250-PIPELINING
> >>    250-SIZE 104857600
> >>    250-VRFY
> >>    250-ETRN
> >>    250-STARTTLS
> >>    250-ENHANCEDSTATUSCODES
> >>    250-8BITMIME
> >>    250 DSN
> >>
> >>
> >> HELO from Dovecot proxy:
> >>
> >>    220 proxy.mydomain.com Dovecot ready.
> >>    ehlo test
> >>    250-proxy.mydomain.com
> >>    250-8BITMIME
> >>    250-AUTH PLAIN LOGIN
> >>    250-BURL imap
> >>    250-CHUNKING
> >>    250-ENHANCEDSTATUSCODES
> >>    250-SIZE
> >>    250-STARTTLS
> >>    250 PIPELINING
> >>
> >>
> >> When a client sends BDAT, Postfix closes the connection. Here's a log 
> >> snippet from Postfix:
> >>
> >>    < MAIL FROM:<user at mydomain.com>
> >>    > 250 2.1.0 Ok
> >>    < RCPT TO:<some at recipient.com>
> >>    > 250 2.1.5 Ok
> >>    < BDAT 114098 LAST
> >>    > 502 5.5.2 Error: command not recognized
> >>    < Content-Type: multipart/alternative; 
> >> boundary=Apple-Mail-55D35F74-2EB7-4B3B-A607-E421DD71C07A
> >>    > 221 2.7.0 Error: I can break rules, too. Goodbye.
> >>
> >>
> >> Apple Mail seems to ignore the fact that Postfix does not understand 
> >> BDAT and Postfix does not like that :-)
> >>
> >>
> >>  From a quick glance at the code it seems CHUNKING is always added to 
> >> the capabilities and that's not configurable. Is this a bug or am I 
> >> doing something wrong?
> >>
> >>
> >> Thanks,
> >>
> >>   Michael
> > 
> > that "may" version depend
> > 
> > http://www.postfix.org/features.html
> > ...
> > Postfix 3.4     SMTP server support for RFC 3030 CHUNKING (without 
> > BINARYMIME).
> > ...
> > 
> 
> As far as I understand, Dovecot always adds certain capabilities. This 
> is the responsible code (I think):
> 
> https://github.com/dovecot/core/blob/c8d03c3cab68328947a5afb47f48aef5b5a1e4ab/src/submission/submission-client.c#L95

Hi!

Thank you for reporting this bug, we'll look into it! 

Aki