Just a wild guess....
Does the sending site have a Cisco PIX in the data stream? If so get
them to insert it completely into the orifice of choice belonging to
the person owning the box.... or alternatively switch off SMTP fixup.
Nigel.
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[ Nigel Metheringham Nigel.Metheringham@??? ]
[ - Comments in this message are my own and not ITO opinion/policy - ]