Per my new Director I setup MS Teams as a standalone thing in O365. It is not in any way connected to our domain outcompany.com. When I set everything up I verified our domain ourcompany.com and was able to set everything up and hand it over to our Director.
About 90 minutes later our on prem Exchange started prompting for a o365 login. This Exchange server runs ourcompany.com for us. It is in no way connected to o365 and I can't seem to figure out why it's happening. We have 13 users testing Teams. We have not purchased anything related to a hosted Exchange solution, just the base package for teams. I can't find any info online describing this issue. Has anyone seen this and can you assist?
Edit:
I have verified that our setup users can email from the o365 portal. This is very confusing since our SPF records should cause these messages to fail. I verified the mail routed through o365 and not our on prem server.