We have an API that sends email. I was trying to set up Exchange O365 so that the API server could send email without authentication. I made some changes and tested and it worked, great! But then I tested from another server and it still worked. Oops. I undid all the changes I made, so it should be back to deployment state, and the relay still works.
Surely this isn't expected, did I miss something?
The steps I took:
- Exchange Admin Center > Protection > Connection Filter > Allowed IP Address: Add server IP
- Exchange Admin center > Mail Flow > Connectors: Added Connector (as described here)
- Admin Center > Domains: Updated SPF record in DNS to include the API server IP address (as described here)
Again, I have reverted all these changes and I can still relay mail through my server using telnet connected to
What else can I check to disable this?