(Following on from Bug 1588391)
Folder URIs seem to be inconsistantly-encoded. And while we can tighten that up (see Bug 124287 comment 26), we'll still need to deal with the inconsistency in existing code and data (eg,
virtualFolders.dat stores folder URIs).
So for now it probably makes sense for the folder lookup service to normalise all lookups,
imap:INBOX/foo bar should equate to
imap:INBOX/foo%20bar (but not to
(And once this is done, we should backout the imap-specific check added by attachment 9101200 [details] [diff] [review]).