For the last month I have been getting these Bad Request(invalid_grant) notices whenever the system tries to send an email. I cant figure out why it is doing this as the connectivity test says that 587 is open. The diagnostic test shows the following:
Postman Sender Domain (Envelope|Message): gmail.com | gmail.com
Postman Prevent Message Sender Override (Email|Name): No | No
Postman Active Transport: SMTP (smtp:tls:oauth2://smtp.gmail.com:587)
Postman Active Transport Status (Ready|Connected): Yes | Yes
Postman Deliveries (Success|Fail): 18 | 44