Link A is exe only, link B is source if you wanna build it yourself.
1692555 bytes (1652 KiB)
23100384 bytes (22 MiB)
The box on the right of the screenshot is the ProtonMail Bridge settings panel.
Step 1 is put the host and port, username and password. and "connect"
Step 2 is select the output path. (it will create each mbox filename based on the folder name. IF you have weird characters in your folder names (is that actually a thing?) then it might not work right, i haven't tried that.
Step 3 is fetch. You get an mbox file for each folder you select.