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.
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.
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