On Prem Exchange 2016 CU 20 Broken By Enabling O365 Teams

Question

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.

Answer 1

I spoke to a MS tech. I was able to open a tech through their online portal.

1. When you activate Teams email comes with it. There’s nothing that can be done about that.
2. Outlook checks for a valid o365 account regularly. If a valid o365 domain exists for the email domain you’re a part of the login prompt will show up and Outlook will expect to connect to o365 as it’s primary connection. This is just how Outlook works now. Not sure if a reg key will fix this one.
3. Our only real option is to build a new domain and at some point migrate our .local to the new domain.

I’ll consider this resolved since I now know that that our solution is a different domain name and the issue was we built the wrong setup.

Answer 2

Sounds like:
https://medium.com/jj365/outlook-issue-with-direct-connect-to-office365-352dd29de65

See the fixes and test it out

Answer 3

We've tried the regedit for testing with no luck. I've now disabled the features via powershell as well. I'm still having the issue.

I found in the approved domains section that it built out an authorative domain for our company. I changed it to relay to try and correct the problem but it hasn't made a difference yet. I can't delete Exchange for some reason. I also can't just shut off Exchange. Seeing as how I didn't buy it, and I don't want it, how do I shut it off? If I purchase a service I expect to get what I paid for, not all this up selling garbage.

Answer 4

@IT Support

I think this issue may related the way that you verify your domain in Office 365. What DNS record that you used to verified your domain? I would suggest you check whether "Autodiscover.domain.com" and "mail.domain.com" still point to Exchange on-premises.

I have verified that our setup users can email from the o365 portal.

Could you provide more tailed information about this one? Do you mean Office 365 admin could send email to your Exchange on-premises?

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Answer 5

I've verified my DNS was all correct. That includes both split and my authoritative DNS service. I see no records pointing to anything we didn't setup.

The emailing from the o365 portal is an odd one. My manager logged into his account on o365 and sent an email to his gmail account and it showed up as his company email address. I checked both our spam service and our on prem service and I don't see the message anywhere. I have custom SPF records setup for our SPAM service. My best guess is that MS did something on their end that got picked up in my include all domain records command on our spf record. I can see no other way that would allow them to email as our domain when they are not in our SPF records.

We deleted our domain off of the o365 portal. Now that it's gone the problem has gone away. Here's my thought on what's occurring. I just need to verify it. Outlook searches for a o365 domain when it loads to see if it's active. If it is then it prompts for the login. We could potentially fix it from the client side if we could get a working reg key fix. The one I tried did not work. The best way to fix it would be to correct it on the o365 side but I'm not sure how to do that.