When emailing CVs or applications I use PDF so there is no concern regarding formatting.
I sometimes do a copy-paste of my CV in the bottom of my email. I have a text-only version that I am sure will show up correctly in the email. I write in the body text that I have done this in case of technical problems. You never know, sometimes people are weary of opening attachments, spam/filter problems, etc. However, this is usually to recipients that have not specifically requested an online CV.
Good luck.