Martin Horak writes:
>> Hello courier users.
I have a problem with courier server - especially SMTP module.
I send a mail through transparent mail proxy on our firewall. When the
primary MX of recipient's domain in unreachable, i get this reply from
relay:
421 4.4.1 Unable to contact destination
There is no such error message in Courier.
Of course, this message comes from our damned firewall/mail proxy, when
remote MTA is unreachable.
Other MX records aren't tried and the mail is deferred. I'd like
courier to contact backup MX'es before deferring the mail.
How can I achieve this?
You can achieve what you want by learning a little bit about SMTP
first. If the above message is received in response to a delivery
attempt, the message is interpreted as an indication of a temporary
failure, and to try again later. That is âlaterâ, and not âtry another
mail relay nowâ. Do to otherwise would be a behavior more akin of a
spam generator, and is likely to get you blacklisted as such
OK, do I have any chance to change Courier's response to this errorcode
(421) from 'try again later' to 'try another relay'?
No, this is not possible.
I really don't want to switch to another mailserver - I'm used to
Courier and i think it has better concept than any other MTA. But this
feature/bug is quite critical for me.
I agree that hijacking a network socket connection, and screwing it up to
the point that the originating endpoint thinks that the connection has been
established, when it really hasn't, is a serious bug.
One more question: In what circumstances Courier falls back to backup
(secondary) MX?
When it cannot connect to the primary MX.
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