I just ran into this with some email generated by my website's code, and wanted to give other authors a heads-up.

My site sends out emails with links delimited by angle brackets that look like this:

<http://example.com/somescript.php?somearguments>

The angle brackets insure that most email clients know where the link starts and ends, even when it gets wrapped over several lines.

When one of my users who uses Yahoo Mail receives such an email, the trailing ">" is rendered as part of the link, so the code that parses it on the website fails. This has been giving me mysterious grief for several sites, particularly with registration and lost password links. It's hard for the user to see, too, as the blue of the link isn't that different from the black of normal text, and spotting the ">" is blue and not black isn't obvious.