Thanks, Martha. As Kitty pointed out, Gretel sent forwards that were readable by using plain text. That sounds like the solution to this.
I use XP with Outlook 2002 at work and I use Thunderbird for my personal mail. My thought was to get a copy of one of these forwarded emails and see if I could find out what was being used for formatting. It could be that the orginal email has some strange formatting or it could be that whatever program is being used on the Mac does something to format the attachment.
But actually all I could probably do is determine that it is unreadable and do something called "strings" on it to see the text within. I doubt that there would be any solution in settings on the end of the receiver that would help. It might be possible to save the attachment if that is how the forward came. But really, the solution is just for the person sending the forward to do what Gretel did, it seems.
If someone using a Mac wants to forward something to me, I'll have a look at it and see if I can find some solution using Outlook or something in Windows. And can see if I can look at the underline code/garbage as well. Otherwise, I have no other answers.
Anita