Thunderbird is the desktop mail program in Mozilla’s orbit: IMAP and POP, calendars, feeds, and OpenPGP built in on the desktop. Mail stays in the program on your machine, which is the real difference from opening Gmail in a browser tab. The Android app is a separate story and still leans on OpenKeychain.
“No telemetry” is too clean. Desktop Thunderbird has data-collection checkboxes under Privacy and Security. Turn them off if you do not want technical and interaction pings going to Mozilla. That is still a different deal from an ad-funded webmail that reads the inbox to sell ads. The window is dense. Extensions can undo the point if you install whatever a forum suggests.
Use it on a computer you control, with those checkboxes off, and with OpenPGP only for people who will actually keep their keys. thunderbird.net
