fx-private-relay

Private Relay is Mozilla's email alias service: give every website a generated address that forwards to your real inbox, and when one starts spamming you, kill it. When an alias leaks, you know exactly who sold you out. The hosted service includes five free aliases, and the code behind it is open source under MPL 2.0.

Self-hosting is technically possible and practically beside the point. It's a Django app that needs Postgres and Amazon SES, plus a sending domain with a solid mail reputation, which is the hard part of any email product. Almost everyone should use Mozilla's hosted service.

Solo users: the free tier plus the browser extension covers the accounts that matter. Premium unlocks unlimited aliases and a custom domain for a few dollars a month. addy.io and SimpleLogin do the same job and are worth comparing before you commit.

The catch: aliases forward mail, they don't host it. You're layering Mozilla's relay between you and every service you sign up for, and if you ever leave, updating hundreds of accounts is the exit cost.