Mail Server Error Message

[Thom Paine]

I jsut got this message on my mail server from one of my users. I'm
not sure about it and I can only find two hits on google, and they are
in french.

451-The server has reached its limit for processing requests from your host

Anyone know what this means? The details of the email are that there
is a user on vacation, and she is forwarding her email to her personal
email address, and this is what we are getting back.

Thanks.

-- 
-=/>Thom