A bunch of question marks in mail

Hey guys,

I am using mail with my work email set as a POP3 account. Sometimes when I forward or reply to an email, my messages get a bunch of question marks randomly through out it. Any ideas why and how to stop it. My boss keeps getting on to me and tells me I need a PC

I REFUSE!!!

The question marks could be anything.
Are you including images in your emails?
What font are you using?
Do you have HTML enabled in your email?

The same questions would have to be answered concerning your boss's email as well.