Yahoo and their mail filters..

Chuck Schick chasjs at
Wed Feb 25 18:18:09 UTC 2009

We found this issue to be associated usually with users forwarding email to
a Yahoo account.  If spam slips by our spam filters and gets forwarded where
the enduser reports it as spam not realizing the impact on their actions.

In the last couple of years we have been not allowing people to forward
their accounts to yahoo, aol, hotmail, etc.  Too much of a headache.


-----Original Message-----
From: Micheal Patterson [mailto:micheal at] 
Sent: Tuesday, February 24, 2009 7:28 PM
To: nanog at
Subject: Yahoo and their mail filters..

This may be old news, but I've not been in the list for quite some time. At
any rate, is anyone else having issues with Yahoo blocking / deferring
legitimate emails?

My situation is that I host our corporate mx'ers on my network, one of the
companies that we recently purchased has Yahoo hosting their domains mail. 
Mail traffic to them is getting temporarily deferred with the "421 4.7.0
[TS01] Messages from temporarily deferred due to user
complaints -; see"

The admin of the facility has contacted Yahoo about this but their response
was for "more information" when they were told that traffic from my mx to
their domain was to being deferred.  I may end up just having them migrate
to my systems just to maintain company communications if we can't clear this
up in a timely manner.

Micheal Patterson

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