How to add email accounts and one account only accessible to one user

Hi @Heike

Thank you for posting your question in Microsoft Q&A. 

We understand you are looking to create an email account for three users to share, along with one additional account for individual use. We recommend using the Shared Mailbox feature, which is well-suited for this setup. Shared Mailboxes don’t require a separate license and allow you to easily manage access permissions.

For 3 users:

This mailbox can be used for general inquiries and shared access among the three users.

For a single user:

Even though it's intended for one person, using a Shared Mailbox is still the most efficient option. It helps avoid the need for an additional paid license. You can simply assign one member to the mailbox, and it will be accessible only by that user.

Note: Once the shared mailbox is set up, it may take some time (up to an hour), the shared mailboxes should automatically appear in each user's Outlook folder list, both on the desktop app and on Outlook on the web.

If it doesn’t show up automatically, users can add it manually in Outlook on the web:

Right-click Folders in the left pane.

Select Add shared folder.

Enter the shared mailbox address and click Add.

You can refer more via: Create a shared mailbox - Microsoft 365 admin | Microsoft Learn

Please feel free to correct me if I misunderstood your request. If you have any additional concerns, feel free to comment below. I would be more than happy to assist.

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