Can I check if an email address exists using .net?

user_378022 0
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Ive seen some php examples of how you can ping an inbox(without sending any mail to it) to check whether it exists. I was wondering if anyone knows if this is possible with .net? If it is Im going to write an app to do a bulk check on list of emails i have captured through my site.

email .net c#
7 Answers

​ 1. Get the MX record for the email provider by using following command:

nslookup -type=mx gmail.com

  1. Make call to tcp client to check if email is valid:

    private static void Main(string[] args)
{            
  var gMail = IsEmailAccountValid("gmail-smtp-in.l.google.com", "aa.aa@gmail.com");
  Console.WriteLine($"Gmail account is valid - {gMail.ToString()}");

  var live = IsEmailAccountValid("live-com.olc.protection.outlook.com", "aa.aa@live.com");
  Console.WriteLine($"Live account is valid - {live.ToString()}");
}

private static byte[] BytesFromString(string str)
{
  return Encoding.ASCII.GetBytes(str);
}

private static int GetResponseCode(string ResponseString)
{
  return int.Parse(ResponseString.Substring(0, 3));
}

private static bool IsEmailAccountValid(string tcpClient, string emailAddress)
{
  TcpClient tClient = new TcpClient(tcpClient, 25);
  string CRLF = "\r\n";
  byte[] dataBuffer;
  string ResponseString;
  NetworkStream netStream = tClient.GetStream();
  StreamReader reader = new StreamReader(netStream);
  ResponseString = reader.ReadLine();

  /* Perform HELO to SMTP Server and get Response */
  dataBuffer = BytesFromString("HELO Hi" + CRLF);
  netStream.Write(dataBuffer, 0, dataBuffer.Length);
  ResponseString = reader.ReadLine();
  dataBuffer = BytesFromString("MAIL FROM:<YourGmailIDHere@gmail.com>" + CRLF);
  netStream.Write(dataBuffer, 0, dataBuffer.Length);
  ResponseString = reader.ReadLine();

  /* Read Response of the RCPT TO Message to know from google if it exist or not */
  dataBuffer = BytesFromString($"RCPT TO:<{emailAddress}>" + CRLF);
  netStream.Write(dataBuffer, 0, dataBuffer.Length);
  ResponseString = reader.ReadLine();
  var responseCode = GetResponseCode(ResponseString);

  if (responseCode == 550)
  {
    return false;
  }

  /* QUITE CONNECTION */
  dataBuffer = BytesFromString("QUITE" + CRLF);
  netStream.Write(dataBuffer, 0, dataBuffer.Length);
  tClient.Close();
  return true;
}

The MX record can be obtained using code:

var lookup = new LookupClient();
var result = lookup.QueryAsync("gmail.com", QueryType.ANY).Result;
var domainName = result.Additionals[result.Additionals.Count - 1].DomainName.Value;

Using above code find the MX lookup and use that MX lookup to check if email is valid or not.

​

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