[baby]

I really don't think so since you're soliciting an email server while a regex is just some code that has to be run, and they are run on a tiny string (a mail is never really long).

Also it's bothering for the user, if you need mail confirmation then do it, but otherwise it should be a RULE OF THUMB to always avoid annoying user. Thus avoid mail confirmation.

This article is actually a really bad advice. I don't know why it's upvoted so much.

[chris_mahan]

I'm not completely sure that I get annoyed when a web site sends me a confirmation email. It helps me know that the site indeed knows my correct email.