Email Verification

Can anyone offer advice on best practices for email address verification? Obviously for user registration it's common to click a link in your email to complete the process thereby verifying the email, but if you want to keep things very simple for the end user, what are the best methods? I have been looking at getmxrr and the examples feature some good advice, etc. One that I've found that I'm thinking of using is http://www.tienhuis.nl/php-email-address-validation-with-verify-probe which tries to connect to the SMTP server as well as mx lookup, etc. How reliable are these? With new domain name extensions appearing all the time I wanted to find something better than a regex which might become outdated after a while and I'd never know about it! Thoughts please and thanks in advance