I've been coding emails for the company I work with for quite some time. My concern is that superscript always looks funky across email clients. The code that I'm currently using is this:
<sup style="line-height:1; vertical-align:baseline;_vertical-align: bottom;position: relative;bottom: 4px;font-size:9px !important;">&reg;</sup>
I vary the font size as needed, and it works in most clients. The two having the biggest issue is Yahoo! and Live. They tend to change the size, as requested, of the superscripted text, but the text is not actually superscripted.

Does anyone here have a better way of doing this? Any help is greatly appreciated! Thank you in advance!