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Re: Abort data transfer?

2009-10-19 11:20:23

Thanks to all who answered this question.

Hector Santos wrote:
SM wrote:
Hi David,
At 14:29 17-10-2009, David MacQuigg wrote:
Is it permissible to abort data transfer before the end of data, say after you have received all headers, and you know the DKIM sig is bad?

RFC-5321 section 3.3 says:

  If the verb is initially accepted and the 354 reply issued, the DATA
  command should fail only if the mail transaction was incomplete (for
  example, no recipients), if resources were unavailable (including, of
  course, the server unexpectedly becoming unavailable), or if the
  server determines that the message should be rejected for policy or
  other reasons.

That paragraph is about the DATA command. You haven't received any headers yet. You don't know whether the DKIM signature is bad. This is more of a SMTP question though. You can do anything you wish for policy reasons. As long as you adhere to the RFC 5321, you won't cause interoperability or hard to debug problems. I suggest not aborting the data transfer to avoid such problems.

+1. Aborted Data transfers can cause retransmissions. Unfortunately, it is better to receive the entire payload and then issue a negative response.

Forget about DKIM. What if there is some other reason to abort, like the payload is too large? We cannot just continue receiving data forever. Is there a "permissible" way within SMTP to abort during data, or should I just ignore these ambiguous requirements, and either: 1) Send a TCP reset, or 2) Let the transmitter hang.

-- Dave