I read an article at CNN.com the other day entitled What your e-mail address says about you, likely inspired by the Facebook messaging announcement. It basically spins through the spectrum of mail services such as aol, hotmail, gmail, etc. and how telling those domains are about the type of person you are. Aol being the least favorable and gmail ranking toward the top. But the article is clear to point out users that use their own domain, user@yourdomain.com, are considered at the top of their mail-o-meter graphic. That is, users that use their own domains are considered skilled and capable.
Now there is nothing official about this article, just some common sense reporting with a little humor. But the fact holds true that having an email address at your own domain lends credibility. Who would you rather let in your home, joescarpetcleners@aol.com or Joe.Smith@TownCarpets.com? Sure, an email is just an email, but it may be the first impression some people have of you. As a web designer, I have clients that, although they have their own domain, still insist on using their old aol, or similar email address.
I have also fallen into this. While I have my own domain email for web design purposes, I use my gmail address for most of my domaining needs. I can't honestly say why I chose to do that over creating a new address at SullysBlog.com. I recognize that it's difficult to make the switch, but it's probably something I should do.
If part of your domaining strategy is to send emails to end users, this could be an important lesson. If you are positioning yourself as a professional and your email address doesn't reflect that, you may be putting potential sales at risk.