Unlimited email addresses for your own domains.
One simple app to organize them all.

Your username is your subdomain.
Also connect other domains of your own. Send and receive emails for any mailbox at your domains. Catches all mail, depending on config.

Assemble a simple but powerful, fully functional, full-stack codebase consisting of only what you need, tailor-made to your specific requirements using state-of-the-art, battle-tested tools you already know. No bloat. No vendor lock-in.