Hello @Max Lorenzoni ,
the synchronization of the Teams calendar with the Outlook calendar only works if this is the same account. In other words, if you also have your Exchange mail addresses with Microsoft. Teams then automatically retrieves the data from Outlook.
I assume that you now also have a hosted Exchange server from yourself or from another provider. This is not possible because Teams does not fetch the data locally from Outlook, but from your Microsoft account. You would have to migrate your Hosted Exchange Mail Server to Microsoft.
Enclosed you will find an overview of the Microsoft Exchange online plans: https://www.microsoft.com/en-us/microsoft-365/exchange/compare-microsoft-exchange-online-plans
If this is helpful, please accept the answer. Thank you.