Fediverse

PCMag seems to endorse it.

Tuta Mail is free for personal use, though you must accept a few limitations. The free edition lets you send and receive all the secure messages you want, and it includes a secure calendar. Searching encrypted email is limited—with the free edition, you can only search messages up to a month old. Paying 36 euros per year for a Revolutionary subscription ($38.65 as of this writing) removes that search limitation, lets you have multiple calendars, and adds features including filtering rules and 15 alias email addresses (more about those later). It also raises the storage for your messages from 1GB to 20GB.