[Mimedefang] Spammers Attacking - I need some help

[Dave Shepherd]

Howdy all,

It seems that my Mimedefang and Spamassassin are pissing some spammers
in China
to the point that they are targeting my company with every possible
combination of user name
they have. As far as I can tell they are all being reject by Mimedefang.

But I am having some problems -

This is how there attack works:
1) they send the message not to my company - but to my ISP's mail relay
via a Yahoo account.
My ISP is listed as an MX mail-relay for my company.

2) My ISP forwards the message to my mail relay running
Mimedefang/Spamassassin

3) My mail-relay rejects the message with "Reject: Message seems to be
SPAM" being
sent back to the sending host (again my ISP).

4) Because the Sending & Receiving address are the same, My ISP then
tries to bounce
the message back to my mail-relay as "Undeliverable"

5) My mail-relay rejects the message again as "User Unknown" or, if it
is a real user (Step 3 above)

I get a copy of all this crap that hits me like a mail bomb in the
Inbox.

I would like to simply discard any email where the $sender and $receiver
are the same. None
of my users should be using this host to send them selves an email. Is
there an easy way to do this?

Or is does anyone have a better idea as to how to deal with this
situation?

HELP !
Dave.Shepherd at Vixel.com
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