The objective is to always keep your email store encrypted in transit and on proton’s server. This is a decryption relay to be used on trusted systems, decrypted with your key. It then serves it up to your email app with startls encryption and an app password, keeping the local store encrypted. Then you can set up your email client to not download a local copy, as you already have a local copy on your local proton store served by your local proton proxy server. I’d argue its more secure than accessing it through a browser, as there is less likely to be malicious add-on activity.
For those unaware, proton mail bridge is a program that sets up a local proton proxy that decrypts the emails then serves them up via a local imap server. Thus the “bridge.” So Thunderbird isn’t pulling from proton, the bridge is pulling the encrypted mailbox and decrypting, Thunderbird pulls from local unencrypted bridge.
The objective is to always keep your email store encrypted in transit and on proton’s server. This is a decryption relay to be used on trusted systems, decrypted with your key. It then serves it up to your email app with startls encryption and an app password, keeping the local store encrypted. Then you can set up your email client to not download a local copy, as you already have a local copy on your local proton store served by your local proton proxy server. I’d argue its more secure than accessing it through a browser, as there is less likely to be malicious add-on activity.