Email Validation C#

There are three levels of validating an email address:

1. Syntax Validation: Does it have an @ sign and at least one full stop, are the left and right hand sides of the @ valid, searching the internet will give you all the things an email address must have.
   http://www.cambiaresearch.com/c4/bf974b23-484b-41c3-b331-0bd8121d5177/Parsing-Email-Addresses-with-Regular-Expressions.aspx
2. Resolve the Domain: You will need to do a DNS MX lookup, there is a nice C# dll on the internet should be easy to find.
   http://aspalliance.com/744_CodeSnip_Resolving_Domain_Names__and_IP_Addresses
3. Use a Socket: Actually go through the process of sending an email and then stop just before issuing the .quit command.
   http://www.eggheadcafe.com/articles/20030316.asp