QMF IMAP support cannot cope with a remote folder delete.

If a folder is deleted from another IMAP client than QMF, then QMF will not delete the folder locally, leading to synchronisation failure and other problems.

To replicate, we had the following setup:
gmail account, QMF mail client

• Create a label titled 'foobar' in GMail
• Sync QMF mail client
• Delete 'foobar' label in GMail
• Sync QMF mail client
• Note that deleted label is still there

This cannot be easily rectified using the QMF client only, as it thinks the folder already exists (so will not create it), instead, we had to recreate the label in GMail, delete from QMF, and then resync.