Dovecot submission announces CHUNKING but backend Postfix does not support it

[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:<u...@mydomain.com>
  > 250 2.1.0 Ok
  < RCPT TO:<s...@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