(.NET Core C#) MailMan GetBadEmailAddrs

Demonstrates how to get the email addresses flagged as invalid during an SMTP send.

Note: An SMTP server can only issue errors for email addresses under it's own domain. For example, if using smtp.gmail.com to send email, the GMail server can only know what emails in the gmail.com domain are invalid. If, for example, the "TO" recipient is "doesNotExist@chilkatsoft.com", then the email would be accepted. If it's not actually a valid email address, it is not flagged as an error during the client-to-SMTP-server conversation. (If the email address turns out to be truly invalid, then a DSN (Delivery Status Notification, or "bounce") email *might* be sent by the final destination mail server to the return address.

Chilkat .NET Downloads Chilkat .NET Assemblies Chilkat for .NET Core Chilkat for Mono

// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// Demonstrates how to get the list of invalid email addresses flagged by the SMTP server
// at the time of sending (i.e. during the SMTP conversation).

Chilkat.MailMan mailman = new Chilkat.MailMan();

mailman.SmtpHost = "outlook.office365.com";
mailman.SmtpPort = 587;
mailman.StartTLS = true;

// Set the SMTP login/password
mailman.SmtpUsername = "OFFICE365-SMTP-LOGIN";
mailman.SmtpPassword = "OFFICE365-SMTP-PASSWORD";

// Create a new email object
Chilkat.Email email = new Chilkat.Email();

email.Subject = "Testing for Chilkat API...";
email.Body = "Testing for Chilkat API...";
email.From = "Chilkat Support <my-office365-user@mydomain.com>";
bool success = email.AddTo("Chilkat Admin","admin@chilkatsoft.com");
success = email.AddTo("Non-Existent Recipient 1","nonexist1@something.com");
success = email.AddTo("Non-Existent Recipient 2","nonexist2@gmail.com");
// To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

// Allow SendEmail to succeed even if some recipients are rejected immediately
// by the SMTP server.
mailman.AllOrNone = false;

// Call SendEmail to connect to the SMTP server and send.
// The connection (i.e. session) to the SMTP server remains
// open so that subsequent SendEmail calls may use the
// same connection.  
success = mailman.SendEmail(email);
if (success != true) {
    Debug.WriteLine(mailman.LastErrorText);
    return;
}

success = mailman.CloseSmtpConnection();
if (success != true) {
    Debug.WriteLine("Connection to SMTP server not closed cleanly.");
}

Debug.WriteLine("Mail Sent!");

// IMPORTANT:  This example uses the Office365 SMTP server.  However, Office365 does not 
// reject any invalid emails, even for it's own domain.  This is common behavior.
// The same is true for GMail.  In many cases, the recipient email addresses are silently
// accepted by the SMTP server, even if known to be invalid.   

// Using GetBadEmailAddrs would only make sense for server that explicilty rejects local recipients
// known to be invalid.

// Examine which email addresses were rejected by the SMTP server during the SMTP conversation. 
// (i.e. during the SendEmail)
Chilkat.StringArray badAddrs = mailman.GetBadEmailAddrs();
int numBadAddrs = badAddrs.Count;
int i = 0;
while (i < numBadAddrs) {
    Debug.WriteLine("Rejected recipient " + Convert.ToString(i) + ": " + badAddrs.GetString(i));
    i = i + 1;
}