class tag in RTE

I would like to have a 'class' tag that is linked to my css inserted into each hyperlink and email that is added inside of a post/reply. 

For instance currently inserts:

<!-- Message body -->
<P>test</P>
<P><A href="http://www.mysite.com" target="_blank">www.test.com</A></P>
<!-- Message body ''"" -->

and I would like for it to do something like:

<!-- Message body -->
<P>test</P>
<P><A class="dash" href="http://www.mysite.com" target="_blank">www.test.com</A></P>
<!-- Message body ''"" -->

Thanks in advance for all the help!