The EndSend event is fired when sending the email message is done. The EndSend event is fired only if the Notifier property points to the EMail object. After the EndSend event was fired, the EMail object releases the Message object. The Message's count reference is increased by BeginSend event, and it is decreased by the EndSend event. In order to check whether the message was delivered OK you must  handle the EndSend event. To check the latest error occurs use the LastError property. Use Error property to get the description for an error code. The following sample shows how to check whether the message was successfully delivered:

Dim WithEvents e As EMail

Private Sub e_Debug(ByVal Msg As EXEMAILLibCtl.IMessage, ByVal Description As String)
    Debug.Print Description
End Sub

Private Sub e_EndSend(ByVal Msg As EXEMAILLibCtl.IMessage)
    If (Msg.LastError = 0) Then
        MsgBox "The message '" & Msg.Subject & "' was was successfully delivered."
    Else
        MsgBox "The message '" & Msg.Subject & "' failed. " & e.Error(Msg.LastError)
    End If
End Sub

Private Sub Form_Load()

    ' Creates an EMail object, that will receive Message notifications
    Set e = Runtime1.NewEMail()
    ' Creates a Message object
    Dim m As Message
    Set m = Runtime1.NewMessage()
    ' Message' notifications are sent through EMail object
    Set m.Notifier = e

    ' Sends a message to one user
    m.Send "me@malibu.com", "robingo@calcuta.fom", "Test", "The message has one attchament", "c:\winnt\system32\setup.exe"
End Sub