B4X

Verify Email Recipients Without Sending

Demonstrates the Chilkat MailMan.VerifyRecips method, which begins the SMTP send process for an email, sends the recipient addresses to the SMTP server, and then aborts before sending the message content. Recipient addresses rejected by the server are returned in the StringArray. This example checks two recipients and lists any that were rejected.

Background: During an SMTP transaction each recipient is offered with a RCPT TO command, and the server accepts or rejects it before any message content is transferred. VerifyRecips exploits that: it runs the transaction just far enough to collect those verdicts, then aborts — letting you validate an address list without actually delivering mail. Note that many servers accept everything at this stage and bounce later, so a clean result is not a guarantee of deliverability.

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Dim success As Boolean = False

'  Demonstrates the MailMan.VerifyRecips method, which begins the SMTP send process for an
'  email, sends the recipient addresses to the SMTP server, and then aborts before sending
'  the message content.  Recipient addresses rejected by the server are returned in the
'  StringArray.

Dim mailman As ChilkatMailMan
mailman.Initialize("mailman")

'  Configure the SMTP server connection.
mailman.SmtpHost = "smtp.example.com"
mailman.SmtpPort = 465
mailman.SmtpSsl = True
mailman.SmtpUsername = "user@example.com"
mailman.SmtpPassword = "myPassword"

'  Build an email with the recipients to verify.
Dim email As ChilkatEmail
email.Initialize
email.Subject = "Recipient check"
email.From = "alice@example.com"
email.AddTo("Bob", "bob@example.com")
email.AddTo("Nobody", "nobody@example.com")

'  Ask the server which recipients it will accept.  Rejected addresses are returned.
Dim badAddrs As ChilkatStringArray
badAddrs.Initialize
success = mailman.VerifyRecips(email, badAddrs)
If success = False Then
    Log(mailman.LastErrorText)
    Return
End If


Dim n As Int = badAddrs.Count
Log("Rejected recipients: " & n)
Dim i As Int
For i = 0 To n - 1
    Log(badAddrs.GetString(i))
Next

'  Note: Explicitly connecting/authenticating is optional.  Chilkat MailMan automatically
'  connects and authenticates -- using the property settings above -- whenever a server
'  operation requires it.  Calling the explicit connect/authenticate methods can still be
'  helpful to determine whether a failure occurs while connecting or while authenticating.