Sometime back we had a discussion (poll?) on "fixing the line length" in our posts. Some, like myself, were of the opinion that the sender should wrap the text at an "appropriate" column, say, 66. Some others were arguing that this scheme only screws up the display.
I just discovered this RFC [http://www.ietf.org/rfc/rfc2646.txt] (have I been living in a cave?) that addresses this issue by introducing a new parameter with the text/plain type. It's "format=flowed|fixed". And guess what - Mozilla already supports it, Mutt is introducing it in 1.3, and Pine developers are thinking about it (I might be wrong, but that's what a recent message on the Pine mailing list suggests).
So I hope this will solve the issue.
Manish