Mail converting entire content to attachments after attaching a file
I have encountered an issue that is really perplexing me.
It seems that just over the last week Mail has started doing something quite strange.
Specs:
Outgoing Mail - OSX 10.6.7, Mail 4.5
Receiving Mail - XP using Outlook 2007 and Windows 7 using Outlook 2010.
Mail server - OSX Server 10.5.8 (All this is internal so it only goes through the one email server)
I can reply and forward several times and attach jpegs along the way with out any trouble.
However as soon as I attach a zip or a pdf or anything that does not display inline it converts the entire message to attachments.
By this I mean that all the footers and reply quotes and message content all converts to separate .htm files and appears as attachments in the receivers Outlook.
So there is nothing in the body of the email and multiple attachments of .htm and .jpg and .whatever.
I have only been able to test this on two Macs both running OSX 10.6.7 sending to two PC's, one running Outlook 2007 on XP and the other running Outlook 2010 on Windows 7. All on the same server as stated above. It is happening externally as well but I have conducted extended testing on the above configuration.
Any clues would be appreciated.