This article applies to:

• Trustwave MailMarshal (SEG)
• Exchange Server

Symptoms:

• Exchange fails to deliver through Trustwave MailMarshal (SEG)
• NDR from Exchange includes the error message: 554 5.6.1 Body type not supported by Remote Host

Causes:

• Exchange is attempting to deliver a message using 8 bit mime.
• 8BITMIME is an optional extension to SMTP (RFC 1652).
• Trustwave MailMarshal (SEG) does not support 8 bit mime, and does not return the 8BITMIME extension response.
• The RFC allows the "undeliverable" (554) response if the destination server does not support this option.

Some versions of Microsoft Exchange attempt to deliver messages using 8 bit mime even to servers that do not advertise the 8BITMIME extension. This is known to occur for messages with attachments that originated on Exchange Server 2007 RTM, as well as messages forwarded through Exchange 2000 and Exchange 2003.

Resolution:

• For Exchange 2007 issues, ensure that Exchange SP1 or above is applied. Exchange 2007 SP1 converts messages to standard 7 bit mime where required.
• You may also be able to reduce this issue by disabling acceptance of 8 bit mime by Exchange. See the following Microsoft resources:
  • Microsoft TechNet resource on receive connector options for Exchange 2007