A project for doing a RFC compliant registration check of an email address.
The pattern to use is this one:
public static string ComplexEmailPattern4 = @"^[\w!#$%&'*+\-/=?\^_`{|}~]+(\.[\w!#$%&'*+\-/=?\^_`{|}~]+)*" // local-part
+ "@"
+ @"((([\w]+([-\w]*[\w]+)*\.)+[a-zA-Z]+)|" // domain
+ @"((([01]?[0-9]{1,2}|2[0-4][0-9]|25[0-5]).){3}[01]?[0-9]{1,2}|2[0-4][0-9]|25[0-5]))\z"; // or IP Address
And now because of the new changes to TLDs, a separate Tld validator is a good idea. So I added one.