Getting emails in which VO just says, object replacement charecter

[Dan Eickmeier]

Hi all, just received an email from a friend of mine, opened it, and I  
don't know whether she had put anything in the body of it or not,  
because all VO had said was, "Object replacement character.  I've seen  
this happen before with some emails, but not from this particular  
person before.  Is this a bug in Mail somewhere?  Or what?