Re: [Exim] Dealing with 451 errors

> >Hello,
> >
> >so it issues a 451 error code.
> >
> >Now, what should site 'B' do in response to this?
>
> From my understanding of SMTP response codes, 4xx is a temporary failure, 5=
> xx is a permanent fatal error.
>
> >Should it sit on the message for a while, periodically
> >retrying it? Or should it immediately fail the message
> >and bounce it back to the original sender as a permanent
> >error? What would Exim do if it was running on site 'B'?
>
> Since the code 4xx indicates a temporary failure, the relaying server shoul=
> d periodically retry it, so when whatever the cause of the 4xx error is res=
> olved, the message can be delivered. Only upon receipt of a 5xx error shou=
> ld the message be immediately rejected by the relaying server.
>
> Jeremy

That's what I was thinking. We have a client who forwards his mail from another
site over to here, and his other ISP's mail server is treating 451 errors as
permanent errors and immediately bouncing them without any retries at all.

Of course, they blame it on us, claiming we should except all incoming e-mail,
even if the sender address can't be verified at the time.

In this particular case it was a transitory DNS issue on the original sender's
end of things, his domain couldn't be verified. 5 minutes later it would have
worked just fine if they'd bothered to retry.

Mark