Review for Hide Local Folders by Nibinaear
Rated 3 out of 5 stars
To go: Tools > Account Settings > Server Settings > Under Message Storage, go to Advanced > Inbox for a different account > Choose "Local Folders".
Now set up a mail rule Under: Tools > Message Filters to move the messages into a folder of your choice.
To create your own collections, you must have a Mozilla Add-ons account.