Thursday, January 15, 2009

Exchange MTA Rewriting Message Bodies

So I got hit up pretty hard by a guy who was quite upset by that fact that we claim to be handling Internet RFC[12]822 e-mail when somewhere along the line, messages were being turned into HTMLified MIME documents. (He even verified by hex dumping his local mail spool)

He claimed that our MTA's were rewriting message bodies and it was a major problem for him that needed to be addressed immediately. He was testing this phenomenon using Mutt as his email client...

From my understanding, by design, once a message reaches an Exchange server it does not preserve the original MIME of the message. When the message gets delivered into Exchange mailbox database it is converted to MAPI format. Then, when MIME is requested for the message from a non-MAPI client the MIME content is regenerated from the new Exchange (MAPI) representation.

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