(VB.NET) OAuth2 for a GMail using a P12 Service Account Key

See more GMail REST API Examples

Note: This example does not work for Personal Google Accounts where the email domain is @gmail.com

For more information, see https://www.chilkatsoft.com/google_workspace_setup_smtp_gmail.asp

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

Dim http As New Chilkat.Http

' --------------------------------------------------------------------------------
' For a step-by-step guide for setting up your Google Workspace service account,
' see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
' --------------------------------------------------------------------------------
' Begin by loading your Google service account key (.p12)
Dim cert As New Chilkat.Cert
Dim success As Boolean = cert.LoadPfxFile("c:/someDirectory/keys/chilkat25-cbd7b42afbd8.p12","notasecret")
If (success <> True) Then
    Debug.WriteLine(cert.LastErrorText)
    Exit Sub
End If


' The ISS is your service account email address ending in gserviceaccount.com.
Dim iss As String = "chilkatsvc@chilkat25.iam.gserviceaccount.com"

' The scope is always the following string:
Dim scope As String = "https://mail.google.com/"

' The sub is your company email address
Dim oauth_sub As String = "bob@yourcompany.com"

' The access token is valid for this number of seconds.
Dim numSec As Integer = 3600

Dim accessToken As String = http.G_SvcOauthAccessToken(iss,scope,oauth_sub,numSec,cert)
If (http.LastMethodSuccess <> True) Then
    Debug.WriteLine(http.LastErrorText)
    Exit Sub
Else
    Debug.WriteLine("access token: " & accessToken)
End If



' The access token allows us to send unlimited emails while it's valid. Once it expires, we must obtain and use a new one.


' -----------------------------------------------------------------------
Dim mailman As New Chilkat.MailMan

' Set the properties for the GMail SMTP server:
mailman.SmtpHost = "smtp.gmail.com"
mailman.SmtpPort = 587
mailman.StartTLS = True

mailman.SmtpUsername = "bob@yourcompany.com"
mailman.OAuth2AccessToken = accessToken

' 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 = "Bob <bob@yourcompany.com>"
success = email.AddTo("Recipient","recipient@example.com")
' To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

success = mailman.SendEmail(email)
If (success <> True) Then
    Debug.WriteLine(mailman.LastErrorText)
    Exit Sub
End If


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


Debug.WriteLine("Successfully sent email using Gmail with a service account key.")