public bool TestEmailRegex(string emailAddress)
{
string patternStrict = @"^(([^<>()[\]\\.,;:\s@\""]+"
+ @"(\.[^<>()[\]\\.,;:\s@\""]+)*)|(\"".+\""))@"
+ @"((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}"
+ @"\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+"
+ @"[a-zA-Z]{2,}))$";
Regex reStrict = new Regex(patternStrict);
bool isStrictMatch = reStrict.IsMatch(emailAddress);
return isStrictMatch;

}

kaynak : http://geekswithblogs.net/VROD/archive/2007/03/16/109007.aspx