[Mimedefang] More than one From address

David F. Skoll dfs at roaringpenguin.com
Tue Aug 23 16:01:01 EDT 2011

On Tue, 23 Aug 2011 14:50:22 -0400
Todd Aiken <todd.aiken at ubishops.ca> wrote:

> In the past 24 hours, I've received a ton of spam at our site.  The
> spam seems to be coming from the same source, in that I see the
> spammer using our domain name as a from address, but they are also
> using multiple From addresses in the same message!  I believe that
> this is non-standard, but it's giving our Exchange server a ton of
> trouble.

It's non-standard, but legal.  See section 3.6.2 of

The From: header is allowed to have multiple mailboxes, but the Sender: header
(if present) can have only one.

> Our Linux gateways are correctly classifying the mail as
> spam, but the transport rules on our Exchange server that filter
> based on the X-Spam-Level header are not triggering because of the
> multiple From addresses, and the spam ends up in everyone's Inbox.
> Is there any easy way I can add something into my MIMEDefang's
> configuration to detect and reject messages that come in with more
> than one From address?

Call Microsoft support and ask them to fix Exchange! :)

You'll have to parse the From: header, I guess.  Use the Mail::Address
Perl module to parse it out and if you get back more than one address,
take action... but be aware that you may block legitimate mail.



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