Here’s a simple workaround for the problem. Download and use MFCMAPI application!
You don’t have permission to create an entry in this folder
The above error message may also prompt you to see the folder owner or ask your administrator to change your permissions. The error mainly occurs because the Contacts folder is flagged as “ReadOnly” by the service during the migration. To fix this, manually set this property for affected users through MFCMAPI. Follow these steps: The MFCMAPI tool facilitates the investigation of Exchange and Outlook issues. It’s been designed for expert users and developers only. Misuse of it or making a mistake could result in the destruction of your mailbox data.
1] Download MFCMAPI Tool
Visit here to download MFCMAPI application from github.com. Start the MfcMapi.exe program that you downloaded, and then click OK.
2] Access Options Menu
When the main window of the application appears, go to the ‘Tools’ menu and select ‘Options’.
Here, scroll down to locate the following,
Use the MDB_ONLINE flag when calling Open MsgStoreUse the MAPI_NO_CACHE flag when calling OpenEntry
When found, select the checkboxes marked against these options, and then click OK.
3] Select the appropriate Microsoft Exchange Message Store
Now, go to ‘Session’ menu, click ‘Logon’.
Then, in the ‘Profile Name’ list, choose the profile for the mailbox, and then click OK.
Double-click the appropriate ‘Microsoft Exchange Message Store’.
4] Change the binary value in Properties pane
When a new window opens, go to the navigation pane, click ‘Root Container’.
Expand Root Container to access ‘Top of Information Store’. Expand ‘Top of Information Store’ and then click Contacts. Now, in the properties pane on the right, look for the PR_EXTENDED_FOLDER_FLAGS property. When found, double-click it, set the binary value to 010400001000, and then click OK. That’s it! The error message You don’t have permission to create an entry in this folder should no more appear for your Outlook Desktop Client. Also read: How to clear Outlook cache files.