Dom Cosgrove Blog

If  you need to validate a email address either through Javascript, server side code or asp.net regular expression validator then the best expression I have found is by Mykola Dobrochynskyy on Code Project.

^(([\w-]+\.)+[\w-]+|([a-zA-Z]{1}|[\w-]{2,}))@” + @”((([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]? [0-9]{1,2}|25[0-5]|2[0-4][0-9])\.” + @”([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]? [0-9]{1,2}|25[0-5]|2[0-4][0-9])){1}|” + @”([a-zA-Z]+[\w-]+\.)+[a-zA-Z]{2,4})$

An example using this would be:

string regEx = @”^(([\w-]+\.)+[\w-]+|([a-zA-Z]{1}|[\w-]{2,}))@” + @”((([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]? [0-9]{1,2}|25[0-5]|2[0-4][0-9])\.” + @”([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])\.([0-1]? [0-9]{1,2}|25[0-5]|2[0-4][0-9])){1}|” + @”([a-zA-Z]+[\w-]+\.)+[a-zA-Z]{2,4})$”;

foreach (string recipient in recipients)
{
if(!Regex.IsMatch(recipient.Trim(), regEx))
{
throw new Exception();
}
}

Reference: http://www.codeproject.com/KB/recipes/EmailRegexValidator.aspx?display=Print