smtp errors

[david902]

using Exchange 5.5 inside my firewall for mail
using MS SMTP 5.0 as a mail relay from the DMZ
into the internal network.

been seeing on my log bounced messages back to the sender

5.6.1 SMTP 554 Body type not supported by remote host.

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most of the messages I see a junk email, get maybe 10/day
just curious as to what is happening and what I need to do to go about fixing it.

thanks

 

[david902]

sorry, the log on the mail relay server in the dmz.