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Re: Remote SMTP error code - missing
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- Subject: Re: Remote SMTP error code - missing
- From: Kyle Wheeler <kyle-qmail@xxxxxxxxxxxxxx>
- Date: Tue, 27 Nov 2007 11:16:38 -0600
- Comment: DomainKeys? See http://domainkeys.sourceforge.net/
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On Tuesday, November 27 at 09:41 AM, quoth Kyle Wheeler:
On Tuesday, November 27 at 11:15 AM, quoth Matt:
I'm quite frequently receiving permanent delivery failures when sending
mail to a particular remote host even though apparently they're responding
with a temporary 45x error. The log entry shows a missing code:
2007-11-26 09:55:26.771462500 delivery 252542: failure: 1.2.3.4_failed_after_I_sent_the_message./Remote_host_said:_Read_timed_out/
Well, the "failure: " indicates a permanent error message, which "proves"
that they sent one, though technically that doesn't completely absolve you
(depending on how logically rigorous you feel like being with the word
"prove").
It's been pointed out to me (thanks James!) that I missed a detail
here. The remote host said "Read timed out", NOT "451 Read timed out"
(because if it had, then qmail would have logged the error code
(unless your qmail has been badly mangled)). Thus, the remote side
isn't *sending* an error code, it's just sending text, which is
invalid. Not checking whether there's a number there, qmail is
attempting to interpret the first three characters as a number. The
way qmail parses, that number will be 3979 (i.e. qmail uses simple
'R'-'0' C logic), which is well above 500, so the response gets
interpreted as a permanent failure.
Technically, this means that your remote side (assuming nobody's in
the middle mucking with the content of your connection) isn't speaking
valid SMTP.
On the other hand, I suppose it's worth pointing out that *most* of
the time, the reason why you'd get a 'Read timed out' error would be
because the client side disappeared (or the network went down), and
informing the client that they've disappeared is a pointless exercise.
That's probably why nobody's ever complained to these folks before.
Anyway, hopefully that helps.
~Kyle
--
Where all men think alike, no one thinks very much.
-- Walter Lippmann
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