O365 w/o exchange

Hi guido290167, 

Thank you for contacting the Tech Community. 

As per the description, after setting up O365, you realized Exchange is setup as well and you want to turn it off. Please note that Exchange Online is part of the Microsoft 365 and Office 365 suite of products. See https://learn.microsoft.com/en-us/exchange/exchange-online

So, the moment you are connected to O365 and you have Licenses that would connect your outlook to the M365 server, then exchange would be setup by default. Meanwhile, if your emails are hosted on a third party messaging platform, but you need to use the O365 Applications alone, then you can proceed to turn off exchange online services when you navigate to the Admin Portal >> Users >> Active Users >> Select the User >> On the right side, click on Licenses and apps >> scroll down to where you have apps >> uncheck Exchange Online. 

I hope this fixes the issues too. If you still have issues, you may reply descriptive screen shots and we'll be happy to help you. 

Thank you.