On Mon, 20 Mar 2017, Peter Leeman wrote:
> Is it possible to block an email if both the sender and recipient domain are the same?
> Example - sender@???<mailto:sender@domain-a.com> to recipient@???<mailto:recipient@domain-a.com>
Mike explained how to do it, but as Nigel said, there will be
consequences.
> The reason I am looking to do this is we are going to be using Exim
> to handle incoming/outgoing mail for a domain hosted on Exchange so
> any mail for domain-a.com being emailed from a mailbox on
> domain-a.com will never leave exchange. We still want a sender on
> domain-a.com to be able to email external domains, but want to
> prevent incoming emails destined for domain-a.com appearing as if
> they are coming from domain-a.com.
I don't think we really know what problem you are trying to solve.
Are you trying to stop the mails from the exchange server going back
still claiming to come from the exchange server, or are you trying
to block mail from outside that appears to come from inside ?
The thing you need to remember is that there will be mail
that starts and finishes on the exchange box that legitimately goes
outside before coming back in - mailing list and forwarded messages.
Some of these will have had their sender addresses changed, but some
will get caught by your trap. What do you want to do with these ?
--
Andrew C Aitchison
