Symptoms:
Changing Outlook IMAP account / reconfigure or enabling "Purge deleted messages when leaving IMAP folders" failed with
"The account name is already being used. Choose another name"
Cause:
Corrupt Outlook Profile
Solution:
Recreate Outlook Profile
Note:
There is quick way to enable "Purge deleted messages when leaving IMAP folders" using regedit (may applicable for other option) without recreate profile
HKEY_CURRENT_USER/Software\Microsoft\Windows NT\Current Version\Windows Messaging Subsystem\Profiles\Outlook\9375cff0413111d3B88A00104B2A6676 (may be different, find with multiple subkeys).
In every subkey check by double clicking "Account Name" to get readable account
create/set DWord key EnablePurgeOnSwitch value = 1
