Hi @Todd Smith ,
I tried deleting and then creating a new Outlook profile in Control Panel,
From the last screenshot you shared above, seems like you selected "Manual setup or additional server types" and choose ExchangeActiveSync, right?
As aforementioned, Exchange accounts can now only be set up through the Auto Account Setup, so please select "Email Account" instead, enter your name, email address and password, click Next:
If this still only sync the old mails back to 2013, add the registry below and then try reconfiguring the mail account again:
Important: Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.
- Open the Registry Editor by typing regedit in the Windows Search or open the run and type regedit.exe.
- Find this location below in the regedit:
HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover - Create a DWORD (32-bit) value for ExcludeExplicitO365Endpoint and change the value to “1” to enable it.
By the way, since your new Exchange server 2019 is hosted by IONOS, I'd recommend reaching out to IONOS as well to see if they have seen similar issues or potential solutions.
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