Gmail Email Attachment Strnage behavior with VB Application

Hello @~OSD~

Have you tried using MailKit, the replacement for Smtp classes.

Microsoft recommends MailKit
https://video2.skills-academy.com/en-us/dotnet/api/system.net.mail.smtpclient?view=net-5.0

Example

You will need to configure setting.
Imports System.IO
Imports MailKit
Imports MailKit.Security
Imports MimeKit
Imports MimeKit.Utils

Public Class Operations  
    Public Shared Async Sub Example1()  
        Dim message = New MimeMessage()  
  
        message.From.Add(New MailboxAddress("Joey", "joey@friends.com"))  
        message.To.Add(New MailboxAddress("Alice", "alice@wonderland.com"))  
  
        message.Subject = "Hello friend"  
  
        Dim builder = New BodyBuilder()  
        Dim image = builder.LinkedResources.Add("C:\Users\Joey\Documents\Selfies\selfie.jpg")  
  
        image.ContentId = MimeUtils.GenerateMessageId()  
        Dim files = Directory.GetFiles("c:\").ToList()  
        For Each file As String In files  
            builder.Attachments.Add(file)  
        Next  
  
  
        builder.HtmlBody =  
            $"<p>Hey Alice,<br>  
<p>What are you up to this weekend? Monica is throwing one of her parties on  
Saturday and I was hoping you could make it.<br>  
<p>Will you be my +1?<br>  
<p>-- Joey<br>  
<center><img src=""cid:{image.ContentId}""></center>"  
        builder.Attachments.Add("C:\Users\Joey\Documents\party.ics")  
  
        message.Body = builder.ToMessageBody()  
  
        Using smtp = New Net.Smtp.SmtpClient()  
  
            AddHandler smtp.MessageSent, AddressOf MessageSent  
  
            Await smtp.ConnectAsync("smtp.gmail.com", 587, SecureSocketOptions.SslOnConnect)  
  
            Await smtp.AuthenticateAsync("Username", "Password")  
            Await smtp.SendAsync(message)  
            Await smtp.DisconnectAsync(True)  
  
        End Using  
  
    End Sub  
  
    Private Shared Sub MessageSent(sender As Object, e As MessageSentEventArgs)  
        Console.WriteLine(e.Response)  
    End Sub  
End Class