Thanks all for the clarification.
You are right. That idea may block more real mail than the spam ones.
From: /dev/rob0 r...@gmx.co.uk
To: postfix-users@postfix.org
Sent: Thursday, February 16, 2012 9:28 PM
Subject: Re: How to block senders whose domain without a MX record
On Thu, Feb 16, 2012 at 05:06:22AM -0800, daniel zhou wrote:
The document segment about the reject_unknown_sender_domain says
that it will reject the domain without A record or MX record. Does
it mean that only domains with both A and MX record will be
accepted? Or, it means any domains with only A record,domains with
only MX record or with both will be accepted. Can anyone clarify
it? Thanks!
An unknown sender domain means that the name did not resolve in a way
such that mail could be delivered to it. An A record, even if it's
0.0.0.0 or 127.x.x.x or any other address that might not be
deliverable for some reason, qualifies as a known sender domain.
Unless of course there is a MX, and that name does not resolve: then
it is unknown. Also a malformed MX record is unknown.
IIRC these rules can be found in RFC 5321 and predecessors.
I just want to block the senders whose domain without MX record,
even if it has an A record.
There is check_sender_mx_access, but I don't know if it strictly
works the way you want. Also, I don't think your idea is a good one.
You will block some real mail, I bet, while making little if any
impact on spam.
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