Verify that email domain exists

Question

Does anyone check the domain of an email address as part of their verification steps? eg. Confirm that gmail.com exists if the user specified blah@gmail.com as their address

Answer 1

You could do a dns lookup on the mx record. Here's an example at Code Project:
http://www.codeproject.com/KB/IP/dnslookupdotnet.aspx

[addendum]:

That should answer your question as asked, but as a side note I agree with @Franci that the old standby of sending a verification message is better. If someone's done everything else right to fool your validation, you're really not buying much in also checking the domain.