I just got a reply on the Microsoft Technet Forum. Here is a workaround to disable the First-Run assistent. I haven’t had the chance to try it out, yet. Maybe someone could give it a try. It’s from Microsoft support.

Exit Outlook.
Start Registry Editor. To do this, use one of the following procedures, as appropriate for your version of Windows.

Windows 10, Windows 8.1 and Windows 8: Press Windows Key + R to open a Run dialog box. Type regedit.exe, and then click OK.
Windows 7: Click Start, type regedit.exe in the search box, and then press Enter.

In Registry Editor, locate and then click the following subkey in the registry:
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Outlook\set up
After you select the key that is specified in step 3, point to New on the Edit menu, and then DWORD (32-bit) Value.
Type DisableOffice365SimplifiedAccountCreation, and then press Enter.
Right-click DisableOffice365SimplifiedAccountCreation, and then click Modify.
In the Value data box, type 1, and then click OK.
On the File menu, click Exit to exit Registry Editor.