Comment 2 for bug 798607

I don't know if this is directly related or a distinct error:

We are using Outlook with an Exchange Server.

My colleague found out, we are missing headers:

In plugin/tiny_xmlrpc.py, you're looking for a MAPI headers tag, which does not exist if the mail was sent locally via Exchange Server connection, without using SMTP as transportation.
For the same reason, no Message-ID headers exists (as _no_ usual internet header exists at all).

Thus strheader = objFields.Item(mapitags.PR_TRANSPORT_MESSAGE_HEADERS) or temp1 = headers.get('Message-ID') would not work.
(If the message came in via Internet connection, we have PR_TRANSPORT_MESSAGE_HEADERS_W, but no PR_TRANSPORT_MESSAGE_HEADERS.