[slightly OT] Fixed column width in Thunderbird

[Chris]

A slight annoyance, but one I'd like to get sorted.

When composing messages in TB I can specify how to wrap the lines to a 
certain length, but it seems this is just for appearance's sake. For 
when the posting appears on the ng the wrapping has gone.

Is there a way to get TB to use hard breaks when 'wrapping' text?
TIA