Firstly, MS did not invent HTML or RTF email.
Secondly, any attachment should not use email. MIME (and others) are inefficient, and not what smtp was designed to transfer.
Thirdly, as I said in an earlier post, it is equally easy to hide a URL in text email - there is a well known way to do this. Its spottable, but then so is a fake html link if your email client is fairly new.
I'm not saying MS's implementation of html or rtf email is ideal - the rtf one in particular did have a few flaws in early days... ...but everyone else's has had issues.
I am certainly not a fan of MS, and really do not like some of the things they are doing with Vista and Longhorn. But I have to concede they are the best option for the vast majority. Hence, I do not buy into this M$ are evil and must be avoided at all costs fad. I deal with many OS vendors - MS, Novell/Suse, Sun Microsystems, RedHat etc, and MS are by far the best for resolving issues, and quickly releasing patches for faults and flaws.