Using older versions of Outlook for Mac in business environments
Dear Daniela
Many thanks for your kind and detailed response,
First of all, I do apologize not to mention about Microsoft Cloud sync on my previous reply. However, when you sync your non-Microsoft account copy of email, calendar, and contacts to the Microsoft Cloud it will allow you to synchronize items between your email provider and Microsoft data centers. Having your mailbox data in the Microsoft Cloud allows you to use new features of Outlook for Mac, such as pinned messages at the top of columns. Therefore, if any non-Microsoft account (IMAP or POP) is added to a new Outlook for Mac and synced with the Microsoft cloud, they will be able to access all features and be considered a Microsoft account. For additional information, you can refer to Sync your account in Outlook to the Microsoft Cloud - Microsoft Support
To answer your question "Could you suggest what this could be about? How Outlook is connected with OneDrive related to IMAP account, what is the main root source of the email? The old version is the main root for OneDrive or?"
Typically, when you switch from Legacy version to the New Outlook, Outlook will migrate your data and sync with Microsoft cloud by default. Therefore, it uses OneDrive as cloud storage to connect to exchange services. However, when you try to add your account manually, it will give you the option to choose whether to sync or not. So, if you select yes, it syncs copies of your email, calendar and contact to the cloud, but if you decline, Microsoft won't store copies of your email, calendar, and contacts for synchronization. As a result, your account on Outlook will be manually added retrieved/synced data directly from your mail provider's server instead of a Microsoft datacenter.
Regarding the new and old versions of Outlook, it depends on which specific versions you are referring to. Generally, newer versions of Outlook have more features and better performance than older versions. However, the basic functionality of accessing email accounts remains the same across versions. In addition, the old version of Outlook downloads and stores a copy of the Outlook data locally, however, the new Outlook stores the data on the cloud. In this case, if you have IMAP and add it manually without syncing to the cloud, the new Outlook will access your Outlook data directly from the email provider's server.
Regarding set the Root inbox in the New outlook for Mac, it is not possible to set the ROOT "INBOX" in the new Outlook for Mac. Also, it is possible that the issue with folder synchronization is related to Microsoft Cloud sync. Therefore, since we have limited permission to collect logs, you may contact our dedicated Outlook for Mac in-app support through Contact support within Outlook for Mac - Microsoft Support. Since they have high privileges and more resources than we have, they will collect your Outlook logs and check to narrow down the issue from their side.
I look forward to your update. Please feel free if you have any questions.
Thank you for your precious time. Have a nice day.
Sincerely,
Libeamlak | Microsoft Community Moderator