You could move your entire profile to an external drive. You can locate account-specific folders on nominated folders or drives. But I can't think of any way to export messages in a way that allows them to be searched by Thunderbird.

I'd consider setting up Local Folders to use your external drive, and use Archives to break large message stores into smaller, year-related folders. Archives in Thunderbird can be searched, but can also be collapsed and largely ignored while you don't need to see them.

markbsschorr said

I have years of of e-mails that are using up space on my hard drive. I'd like to move them all to an external drive, but with the ability to access them if needed. These messages are currently in my Local Folders. Can this be done?

My Case is similar: My desire is to be able to move bunches of messages into a "cold-storage" file (or a set of such files), so that they are not in the live folders of the account, and at a later time, bring that folder back into action.

I can conceptually visualize some method by which I could create a folder for the purpose, then grab messages which I want out of the way, and using the ordinary "move" - put them into that custom folder. Imagine (in the physical, real-life) bringing a truck to the office, and loading the filled boxes into it - which then carries them away to "the warehouse". If I ever need access to those, I could later bring the (probable) folders back INTO the set of active folders, so they are again in ordinary mode.

MarianGB