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Subject: Re: reject_unknown_sender_domain flawed?
From: Wietse Venema (wietseporcupine.org)
Date: Sun Jul 02 2000 - 17:34:05 CDT

Rask Ingemann Lambertsen:
> Den 02-Jul-00 21:17:47 skrev Wietse Venema f_lgende om "Re: reject_unknown_sender_domain flawed?":
> >Rask Ingemann Lambertsen:
>
> [cut patch]
> >This seems wrong to me. If a DNS server is busted so that sender
> >MX lookup fails but sender A lookup succeeds, then Postfix should
> >not reject the mail as if the sender domain is unknown.
>
> >There is a reason why Postfix DNS lookups for receiving mail are
> >different from Postfix DNS lookups used for delivering mail. The
> >reason is that Postfix receives mail instead of delivering it.
>
> The whole purpose of having the reject_unknown_(sender|recipient)_domain
> checks is to only accept domains to which we can deliver mail, isn't it?

No. The purpose is to reject mail from domains THAT DO NOT EXIST.

In order to find out if mail is deliverable, one has to connect to
an SMTP server, deliver a probe message, and see if that message comes
back within a day or so as undeliverable. That is clearly unpractical.

Therefore I am only concerned about existence, not deliverability.

> >ignore_mx_lookup_error is for *sending* mail not receiving.
>
> See above.

Oh well.

        Wietse