We asked the question in the past, Can an Email Address Be Counted as a Back Link? Well, maybe the answer is yes.
As you can see from the image below (if you can't see, click on it for a larger view), Yahoo is showing that they indexed an email address and they consider it a link. Why?
So I clicked on explore URL, exploring the email address, and it showed me there is a link from this email address at my personal blog.
So I clicked over and noticed, my client accidently put his email address in the location of the web address for when he commented.
So, technically, it is wrapped in an <a href=" but it is also linking to sales@excel and the @ symbol should make it invalid. However, my server people must have made it work, because when I try that URL in my browser, it works fine.
So, clearly this needs to be 301 redirected. But should Yahoo! know better? Nah, I'll take the blame for this.
Technically, Yahoo! is indexing a link and not an email address. So I have yet to see evidence of an email address that can earn link popularity.
Forum discussion at Search Engine Roundtable Forums.