(VB.NET) Office365 Send Email using SMTP with OAuth2 Authentication

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Demonstrates how to send email from smtp.office365.com using OAuth2 authentication.

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' An Office365 OAuth2 access token must first be obtained prior
' to running this code.

' Getting the OAuth2 access token for the 1st time requires the O365 account owner's 
' interactive authorization via a web browser.  Afterwards, the access token
' can be repeatedly refreshed automatically (with no user interaction).

' See the following examples for getting and refreshing an OAuth2 access token

' Get Office365 SMTP/IMAP/POP3 OAuth2 Access Token
' Refresh Office365 SMTP/IMAP/POP3 OAuth2 Access Token

' First get our previously obtained OAuth2 access token.
Dim jsonToken As New Chilkat.JsonObject
Dim success As Boolean = jsonToken.LoadFile("qa_data/tokens/office365.json")

Dim mailman As New Chilkat.MailMan

mailman.SmtpHost = "smtp.office365.com"
mailman.SmtpPort = 587
mailman.StartTLS = True

' Use your Office365 email address for the SmtpUsername.
mailman.SmtpUsername = "OFFICE365_EMAIL_ADDRESS"
mailman.OAuth2AccessToken = jsonToken.StringOf("access_token")

' Create a new email object
Dim email As New Chilkat.Email

email.Subject = "This is a test"
email.Body = "This is a test"
email.From = "MY_NAME <OFFICE365_EMAIL_ADDRESS>"
success = email.AddTo("John Doe","somebody@example.com")

' Call SendEmail to connect to the SMTP server and send.
' The connection (i.e. session) to the SMTP server remains
' open so that subsequent SendEmail calls may use the
' same connection.  
success = mailman.SendEmail(email)
If (success <> True) Then
    Debug.WriteLine(mailman.LastErrorText)
    Exit Sub
End If


' If SendEmail failed because of "Failed to get initial SMTP Response", then it may be 
' a firewall or anti-virus blocking communications.
' See https://cknotes.com/smtp-office365-com-failed-to-get-initial-smtp-response/

success = mailman.CloseSmtpConnection()
If (success <> True) Then
    Debug.WriteLine("Connection to SMTP server not closed cleanly.")
End If


Debug.WriteLine("Mail Sent!")