e-mails on Emacs: #1 - #2 - #3 -#4

AKA isync. Available on Linux with sudo apt-get install mbsync.

Example

Assuming you are using protonmail/bridge. Create the directories ~/Mail/proton. Then create a file called ~/.mbsyncrc and put the following content in it.

IMAPAccount protonmail
Host 127.0.0.1
Port 1143
User (your email)
Pass (your bridge password)
SSLType NONE

IMAPStore proton-remote
Account protonmail

MaildirStore proton-local
Subfolders Verbatim
Path ~/Mail/proton/
Inbox ~/Mail/proton/INBOX/

Channel proton
Master :proton-remote:
Slave :proton-local:
Patterns *
Create Both
SyncState *

Then run

mbsync -a

Explanation

The first part defines the account details. The second and third parts define the remote and local stores. The fourth part defines a channel and master-slave settings (called far-near in the new version, lol).