Mozilla Thunderbird uses the mbox format, which makes it incredibly portable and easy to process. Unfortunately, it also means that all of your messages within a Thunderbird folder is in single file*. This can cause problems if you keep using a folder for many years. For instance I have a mbox file that is >1GB and it’s mounted in a network share. Opening, modifying, backing up takes quite a while. I finally gave up and decided to do something about it.
I wanted to organize my mailbox by year, while preserving its folder organization. A quick online search did not find anything I can use. So I whipped up my trusty PHP and wrote this.
Usual disclaimer applies.
* I’m simplifying here. If your folder contains subfolders, each subfolder actually has it’s own file