If you see any stray IMAP folders that are greyed out in Thunderbird, these may be folders that no longer exist on the mail system but they show up in your client as dead folders. These may be due to synchronization issues between multiple clients. Follow these steps to clear it
- Right click on the account (ex. username@psmail.net) in the folder pane
- From the popup context menu, select ‘Subscribe…’
- A ‘Folder List’ menu pops up
- Scroll the list for folders that have a bullet (i.e. no โ) to the right
- Click the bullet to change it to a check mark
- Repeat as necessary
- Click ‘OK‘
Check to make sure all the IMAP folders are proper, to cross-check login at https://mail.psmail.net/ and compare to make sure all is current and to up to date. If there is discrepancies, repeat the steps highlighted above.