Forum Discussion
bulk sender
When I say send to clients from bulk sender program Using smtp office365 Delivery has failed to these recipients or groups: mailto:gps.gav@ntlwo...
Using Office 365 to send bulk messages is a bad idea, and will result in the exact behavior you are observing - your user(s) or even tenant being blocked from sending messages. Use a service that specializes in bulk sending instead, or spin up a mail server.