Mark Scholten:
> Hello,
>
> Should a system that gives the following response to a SMTP request give a
> code 450 error or a code 550 error (I did think a code 550 should be given).
>
> (host mxfilter4.domain.net[70.34.y.z] said: 450 4.1.1 <u...@domein.nl>:
> Recipient address rejected: undeliverable address: host
> mail.domein.nl[70.34.x.y] said: 550 "Unknown User" (in reply to RCPT TO
> command) (in reply to RCPT TO command))
>
> I did change domain names and the email address and IP addresses (as they
> aren't needed in this example and pointing to someone is also something I
> don't want to do).
>
> Is what I suspect correct or are I wrong?
> Current situation:
> - it gives a 450 error code (while it receives a 550 error code)
> I think it should be:
> - it should give a 550 error code (because it did receive a 550 error code
> from a server downstream)
You can configure Postfix to reject such mail or to reply with
4xx. In the latter case you get a chance to make a whitelist entry
for sites that send legitimate mail with a non-replyable address.
Wietse
