Thank you for bringing this up. Very interesting reading about this issue. Learn something every day because of this place :)
I had an issue with this a long ways back and eventually gave up trying to insert the contents into the body of the email, instead programmatically attaching a file of the text and sending it off that way.
Apparently, there is ~1k limit on each line of the message body, so if you just put in a few well placed Carriage Return Line Feeds(every < 1k), that should fix your problem.. the limit for the body is set at the mail server, and most are > 5MB.