[exim] Mail servers blocking DSN's

Hello,
I have just came across two servers that are blocking empty envelope
to's

VIZ
telnet mail.ophosting.net 25
Trying 63.246.16.254...
Connected to mail.ophosting.net.
Escape character is '^]'.
220 ophosting.net (IMail 8.00 37307-38) NT-ESMTP Server X1
helo itsme
250 hello ophosting.net
mail from:<>
501 bogus mail from
quit
221 Goodbye
Connection closed by foreign host.


I assume that this is some kind of anti spam measure
So this means
1. They will never get a DSN
2. sender callout will fail


Now obviously if they do not accept DSN's undeliverable messages will
be frozen on our server and so this should be rejected. Personally I
would be quite happy to leave it at that. However one of my clients
wants to be able to receive mail from two such domains.

So I was wondering if anyone else has came across this strange tactic. ?
If it becomes more widespread then perhaps we need an option to
specify the from address in sender callouts.

That way if you are using callouts as an anti spam measure then you
can use postmaster as the sender.
and retain some of the advantages.
The only problem with having a from address in the callout is that
you might get a mail callout loop if the other server is doing call
backs. Hmmm thats a big problem.

Perhaps there should be a way to defer if the from is rejected as
opposed to the rcpt to:


Comments ?


Stuart Gall