The Outlook program has to orchestrate the migration and there is always a chance something is going wrong with the cache of the Outlook mail program. In my case, the migration of my mails meant that over 100.000 emails were transferred from one mailbox to another in a matter of hours. Property is not valid for this object type. ChangeKey is required for this operation.

Operation would change object type, which is not permitted. Right-click on the account in the navigation pane > Then, choose the Properties option > Then, click on the Empty Cache option > Now, right-click on the folder containing the email attachments that aren't downloading and select Synchronize Now. Here are some examples of error messages that I have observed: There error messages contained the information about the mail (the subject line), the time at then the error in the synchronisation happened, the error message itself, the details of this error message and some kind of cryptic error code. Unfortunately, some of the mails that were migrated showed up in the Sync Error dialog and reported some kind of error message. In order to migrate the whole mailbox from one account provider to the other, I used Microsoft Outlook for Mac device running the latest macOS operating system and Outlook 16.6 (latest version at the time of writing this blogpost). This migration also meant I had to move over all of my existing emails from Google to Microsoft. Recently I made the switch from Google Gmail to Microsoft Outlook for my personal emails. Blank window opens for up to fifteen seconds then shuts without warning.

Outlook for mac not working