Hi Chris,
I use TextPad (
TextPad - the text editor for Windows) for email formatting. You can try the free, unlimited trial download of TextPad
You can set the line length under the Preferences, according to file type. There is an option for word wrap that forces hard line breaks when you save.
I've found that if I cut and paste my TextPad text BEFORE saving, my line breaks are not preserved. Maybe this is what's happening to you.
If you want to be sure of getting the hard breaks, save your file, then open it again to copy. Experiment.
--Karl