Android Question Email sending by Net, SMTP

Private Sub Button1_Click
    xui.MsgboxAsync("Hello world!", "B4X")
    smtpClient.Initialize("smtp.gmail.com", 587, "xxxxx@gmail.com", "xxxxxx", "SMTP")
    smtpClient.StartTLSMode = True
    smtpClient.To.Add("xxxxxx@gmail.com")
    smtpClient.Subject ="Test subject"
    smtpClient.Body ="TestingBody"
    Dim sf As Object =      smtpClient.Send
    Wait For (sf) MessageSent (Success As Boolean)
        
    If Success Then
        xui.MsgboxAsync("OK", "B4X")
    Else
        xui.MsgboxAsync("Error", "B4X")
    End If
End Sub

 Wait For (sf) SMTP_MessageSent (Success As Boolean)
If Success Then
  Log("ok")
Else
 Log("error: " & LastException)
End If