Sending ICS Calendar File by Email Vb.net - vb.net

Question

When I send a calendar file by email, it appears correctly on recipient's email. When I send same file programmatically, it does not. here is what I do programmatically
Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim Mail As New MailMessage
Mail.Subject = "test email"
Mail.To.Add("someuser#gmail.com")
'Mail.To.Add("somesender#gmail.com")
Mail.From = New MailAddress("somesender#gmail.com")
Mail.Body = "This is a sample email using VB.NET"
Dim attachment As System.Net.Mail.Attachment
attachment = New System.Net.Mail.Attachment("C:\Users\x\Downloads\testCalendar.ics")
Mail.Attachments.Add(attachment)
Dim SMTP As New SmtpClient("smtp.gmail.com")
SMTP.EnableSsl = True
'SMTP.DeliveryMethod = SMTP.DeliveryMethod.SpecifiedPickupDirectory
SMTP.Credentials = New System.Net.NetworkCredential("somesender#gmail.com", "password")
SMTP.Port = "587"
SMTP.Send(Mail)
End Sub
here is the content of the test ics file
BEGIN:VCALENDAR
VERSION:2.0
BEGIN:VEVENT
DTSTART:20160930T110000
DTEND:20160930T120000
SUMMARY:Bastille Day Party
LOCATION:123 Main Street, Anahiem CA
DESCRIPTION:THIS IS A TEST DESCRIPTION
END:VEVENT
END:VCALENDAR
Any ideas?
thanks

Answer 1

There is absolutely no way to do this using System.Net.Mail as the resulting MIME message content will have the wrong structure. The VCalendar information needs to be contained within a specific MIME part but it will be placed in a separate one and treated as a normal attachment.
I wrote my own SMTP client and MIME message generator specifically to overcome this issue by creating the MIME content exactly as is required. The issue with doing this was that I needed to cater for different security protocols, such as NTLM, which was a pain to code.
You may be able to find a third-party SMTP client that supports the behaviour you require in the nuget gallery.