Re: external host [xxx.xxx.xxx.xxx] attempted to send as my domain

From: Murray S. Kucherawy <msk_at_blackops.org>
Date: Fri, 29 Jun 2012 21:29:56 -0700 (PDT)

On Fri, 29 Jun 2012, Jim Fenton wrote:
> I presume that you mean an external host that is sending messages
> without a valid DKIM signature for your domain. They shouldn't be able
> to send messages with valid signatures from your domain.
>
> You might want to be careful about rejecting such messages. If you have
> users who send through external mailing lists that break DKIM
> signatures, they might not receive list messages from others in your
> domain.

Hi Jim,

The issue is a machine trying to send mail either to your server or
through it using a domain name in the From: field that is one for which
you would normally add a signature, except that the SMTP client isn't on a
network you've labeled as "internal". OpenDKIM whines about this in the
log as a possible security concern, and doesn't sign the message.

-MSK
Received on Sat Jun 30 2012 - 04:30:14 PST