When the backup job completes the Job notification is never received.
Error: Unable to connect to the remote server
Job completes with no Error, but you do not receive a notification email. This can be caused by:
Email relay server blocking emails that exceed 512KB size
The email is being blocked by the email filter
Email Notifications are configured incorrectly
When Veeam sends the E-mail for job completion it is sent from the proxy that is configured in the job. The test email will only check the connection from the Veeam Office 365 server to the SMTP and not the proxy. Ensure that the Proxy chosen in the Job settings has access to the SMTP server.
When Veeam Office 365 connects with the SMTP server to send the mail but we do not wait for a confirmation that the email was sent. If this message was rejected for any reason there will be no error from our console. Check email relay settings and spam filter for quarantined email around the time the job completes