One of my pet peeves with Front Page was that it didn't handle dynamic Share point links. When you needed it to place a variable into the URL, it would change the hyperlink to an email address.
I am of course assuming that you want the email link in the middle of a web-part. Well, this answer will work in a web part or not.
Unfortunately, when SP Designer came in, I thought, "oh, all the good that is Front Page minus what is bad", oh was I wrong. Sure, it has new features, but c'mon, lets get the bugs out first ok?
Anyway, onward:
Open the document you want to contain the email link in SP Designer.
Right-Click the web-part that contains the text you want to link, and click 'convert to XSLT Data View'
Select the link text (text you want to insert the email link).
Right-click, select 'hyperlink'
type XXX as the address.
Click OK.
Click 'Code View' (lower left corner of the screen).
Move to the top of the document ([CTRL]+[HOME])
Search for 'xxx'
You will see code like this:
<a href="xxx"><xsl:value-of disable-output-escaping="no" select="@ProjectType"/></a>
Change 'xxx' to whatever you want, such as:
<a href="mailto: President.bush@whitehouse.gov? subject=DST& body=Are%20You%20Kidding%20Me...">
Save your document.