Smtp.SendMessage returns Nothing

Question

I am using VB.net.
when i want to send an email with

Dim result As ISendMessageResult
result = smtp.SendMessage(email)

and for example because of a wrong emailadress, sending fails.
The returnvalue is NOTHING instead of a regular value.

and because of NOTHING, i can't handle any Errors because i don't get any
Values back.

How can i detect what has been the reason why sending failt.

Please help

Here is my extracted code:

Dim lngBytesSent As Long, ResponseText As String 
', I As Integer, wert As String, response As SmtpResponse

builder.LoadHtml("MSG-Filename")
builder.Subject = "Test"
builder.From.Add(New MailBox("Sender@domain.de", "Sender@domain.de"))
builder.[To].Add(New MailBox("rec1@domain.de", "rec1@domain.de"))
builder.[To].Add(New MailBox("rec2@domain.de", "rec2@domainxxx.de"))
Dim email As IMail = builder.Create()

Using smtp As New Smtp()
    Try
        smtp.AllowPartialSending = True
        smtp.Connect(mSMTPServerName, mSMTPServerPort)    
        ' or ConnectSSL for SSL
        If mSMTPAccountName = "" Then
        Else
            smtp.UseBestLogin(mSMTPAccountName, mSMTPAuthPWD)
        End If
    Catch ex As Exception
        smtp.Close()
        Exit Sub
    End Try

    Dim result As ISendMessageResult
    Try
        result = smtp.SendMessage(email) 
        'with a wrong reciepient an error is thrown

        If result.Status = 0 Then
            MsgBox("result.Status = 0")
        Else
            If result.Status = 1 Then      
                'Partial success status: message was succesfully 
                'sent to some, but not to all receipients
                If result.FromRejected Then
                    MsgBox("result.FromRejected")
                Else
                    If result.RejectedRecipients.Count <> 0 Then
                        MsgBox("result.RejectedRecipients.Count <> 0")
                    Else
                        SendStatus = 4  'Socket closed
                        ResponseText = Get_ResponseText(result.AllResponses)
                    End If
                End If
            Else   'keine email ging raus, Failure status: message sending failed

            End If
        End If
    Catch e As SmtpResponseException
        'error handling never reaches this section WHY !!!!
        MsgBox(e.Response)  '
        If IsNothing(result) Then
            MsgBox("result.Status = Nothing")
        Else
            If result.Status = 2 Then   
            'keine email ging raus, Failure status: message sending failed
                MsgBox("result.Status = 2")
            Else
                MsgBox("result.Status = 1")
            End If
        End If
    Catch ex As Exception
        MsgBox(ex.Message)
        If IsNothing(result) Then
            MsgBox("result.Status = Nothing")
        Else
            If result.Status = 2 Then   
            'keine email ging raus, Failure status: message sending failed
                MsgBox("result.Status = 2")
            Else
                MsgBox("result.Status = 1")
            End If
        End If
    End Try
    smtp.Close()
End Using

with a wrong receipient i always end up in the 'Catch ex As Exception' section. and result is NOTHING.

Thank you for your immediate response.

Comments

Could you please show your code?

---

First: consider using enums, such as SendMessageStatus.Success, SendMessageStatus.Failure instead of integers.

Answer 1

Unless you encounter serious SMTP protocol error - in which case a SmtpResponseException or ServerException is thrown, return value of Smtp.SendMessage method is always non-null

[Edit]
After looking at your code:

1. If you are ending in 'Catch ex As Exception' block, it most likely mean that your server disconnects when it encounters incorrect recipient - this violates SMTP protocol obviously, but some servers act in such way. The expcetion is a ServerException in such case.

   You can turn on logging to get more info:
   https://www.limilabs.com/blog/logging-in-mail-dll

2. In 'Catch ex As Exception' block, 'result' variable can not be set - this is how .NET and VB.NET works.

3. You can examine ex.Data["SendMessageResult"] entry to get ISendMessageResult in such case. This entry is filled only if a problem happened after Mail.dll tried to send a message (e.g. during RSET command)