Fastmail is an email service offering a privacy-focused, user-centric alternative to free email providers like Gmail.
It has everything you would want from an email service: web and mobile apps, contacts and calendar support, integration with other clients using IMAP and CalDAV/CardDAV protocols. And it has nothing that you don’t want, like ads or being tracked along with the rest of your web activity. It even has a streamlined feature to import all your email, calendars, and contacts from Google and many other email providers.
Although it’s not free, you pay per user account, not per address or domain. Because Fastmail supports custom domains, all of my domains forward to the same account, using wildcard, so I have effectively infinite email addresses but only pay for one account. I even have my Gmail account set up to forward to Fastmail, as I transition the email address on all of my online accounts to use Fastmail address(es).
Because email is a core feature and product for Fastmail, they care a lot about email standards, and even helped develop a new protocol, JMAP, which has been accepted by the IETF as an Internet Standard (RFCs 8620 and 8621.
I’ve talked before about Hey, which seems promising for me once it supports custom domains and some other features. But for now, Fastmail is the email service I use every day.