Offlineimap becomes quite slow when you have so many (empty folders), this is how you can delete them.
The blog post is based on a (now offline) article by Matt Palma.
Besure to double and triple check every command, actions on the remote are permanent. If you want to read more about the dangers of deleting stuff, read the Matt Palmers article.
Find all empty folders
cd Mail/ # or wherever you put your Mails for i in INBOX.*; do find "$i" -type f | grep -q "$i" || \ (echo "$i" ); done >/tmp/empties cat /tmp/empties
Review the file list
Remove empty folders locally
cat /tmp/empties | while read i ;do rm -rvf "$i" done
The code snippet supports folders with spaces.
Remove empty folders via offlineimap remotely
This is where we use offlineimap instead of logging into the remote server.
cat /tmp/empties | while read i ;do offlineimap --delete-folder "$i" done