Copy the text and paste it into Notepad, or another plain ASCII text editor. Use plain ASCII in your e-mail, not HTML. The more coding you insert (fonts, size, HTML), the greater the chance of funky formatting on the other end. Notepad will simplify the program, stripping out all of the special codes and characters Word and other word processing programs insert. Then copy from Notepad and paste into an e-mail.
Normally, you would
underline to denote italics. In a body-of-email sub, simply add an _underscore_ to either side.
Double space between paragraphs, and don't bother to indent.
A lot of body-of-email places will have specific submission guidelines as well. (See
Strange Horizons, for a pretty good and easy-to-follow example.)
Needless to say, if the market's guidelines contradict what I say, go with their guidelines.
Oh, and do e-mail a copy to yourself before you send it out, to make certain nothing strange happens that didn't show up when you composed the e-mail.