I completely forgot that I had a blog.
I receive a tremendous volume of email and, for work, am tired of maintaining IMAP folders and filter rulesets except for the most voluminous of mailing lists. Especially when situations change and I'm forced to move mail around.
I like to keep everything in one big pot - the Inbox - but still want organization. Mail.app has "Smart Mailboxes" which is intuitive and easy to use (albeit sometimes slow). Essentially it is a saved search that is displayed as a folder and can comprise any number of search criteria. Thunderbird at different times referred to them interchangeably as Favorite, Smart, Virtual, and Saved Search folders.
As good as Mail.app is, however, I returned to Thunderbird for several reasons (tabbed messages being one) and sought to recreate this environment. But Thunderbird has been inconsistent across releases on how to create Smart folders, the method is not intuitive, and documentation on the subject is pitiful.
Here's how it's done using Thunderbird v.3.1.7 on OS X:
1) Initiate a search using either cmd+shift+f or from the menu bar: Edit->Find->Search Messages...
Note that searches must be performed this way and not via either the Search or Filter bars.
2) Enter your search criteria and then select "Save as Search Folder"
3) Create the Smart folder Name, specify where on the tree it will be a subfolder, and double-check the search criteria.
4) Hit OK and you're done.