RegexUtility.IsValidEmail MSDN example as PowerShell

IsValidEmail.ps1

Add-Type -Language CSharp -TypeDefinition @"
using System;
using System.Globalization;
using System.Text.RegularExpressions;

public static class RegexUtilities
{
    // Examines the domain part of the email and normalizes it.
    private static string DomainMapper(Match match)
    {
        // Use IdnMapping class to convert Unicode domain names.
        var idn = new IdnMapping();

        // Pull out and process domain name (throws ArgumentException on invalid)
        var domainName = idn.GetAscii(match.Groups[2].Value);

        return match.Groups[1].Value + domainName;
    }

    public static bool IsValidEmail(string email)
    {
        if (string.IsNullOrWhiteSpace(email)) { return false; }

        try {
            // Normalize the domain
            email = Regex.Replace(email, @"(@)(.+)$", DomainMapper, RegexOptions.None, TimeSpan.FromMilliseconds(200));
        }
        catch (RegexMatchTimeoutException) {
            return false;
        }
        catch (ArgumentException) {
            return false;
        }

        try {
            return Regex.IsMatch(email,
                @"^(?("")("".+?(?<!\\)""@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@))" +
                @"(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-0-9a-z]*[0-9a-z]*\.)+[a-z0-9][\-a-z0-9]{0,22}[a-z0-9]))$",
                RegexOptions.IgnoreCase, TimeSpan.FromMilliseconds(250));
        }
        catch (RegexMatchTimeoutException) {
            return false;
        }
    }
}
"@