Hello there Jaya jay. '''Imap''' Are you seeing greyed-out sections? This can happen if Thunderbird limits concurrent connections to prevent server instability. What account protocols (IMAP/POP) are you using? Try to use the local storage trick: right-click on the local folders > select new folder in that present pane > give it a temporary name > go to the source account and click on all messages and choose 'copy to local folder' > new local folder. Always copy first then move it. '''''Note''''' If this process fails >don t worry you won t lose data. Once you have copied all data safely to that new local folder, it's time to go to the other account, create a new folder there too, copy all data into that, and move it to new folders / folder from there. '''''Add-on issue''''' If you have issues creating folders, it could be caused by bad add-ons. Try using troubleshooting mode to identify them, then update or remove them. '''''Try''''' Restart your computer and app to fix temporary bugs. If issues persist, try repairing the parent folder, ensuring there is enough free space (inbox too) and that the folder is not overfull. Select the parent folder if you want to use the repair folder. '''''Tip''''' You cannot add sub-folders to a mailbox . '''''Use''''' https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird Can you get through this process?