Author: Ted Cooper Date: To: exim-dev Subject: [exim-dev] [Bug 1066] interpret some 4xx error codes from remote
server as permanent errors (5xx). Sometimes the Postfix MTA returns 4xx
error when mailbox does not exist
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--- Comment #16 from Ted Cooper <eximX0902w@???> 2011-01-16 14:04:42 ---
I'm sorry, but this is insane. We're talking about deliberately coding to allow
for blatant abuse of the SMTP protocol here. Even if it's hidden away, this
just allows for too much abuse.
If the other end is configured to sent 4xx, it should be treated as such. If
you know that a server is returning an erroneous 4xx when it should be
returning a 5xx, add some specific retry rules and contact the postmaster to
fix their server. A temporary fix to something that is a misconfiguration.
If the other end is configured to send 5xx, again, it should be treated as
such. If someone gets a 5xx from my servers and instead of leaving it alone
keeps on trying to send again and again, I'll put them in the same bucket as
all the other connections that looks like that - spammers.
Well known and expected behaviour is the only way that these protocols continue
to work. The codes are not up for interpretation. 4xx is temporary, 5xx is
permanent. If mail admins have configured their mail servers to return those
codes, they have to be respected. There's no way to second guess things