Oh. And personally I am using mailbox.org which is also nice but a little bit cheaper. And the feature-set is still great, but limited compared to FastMail. Also the webui in mailbox.org is slower than for fastmail.
Fastmail becomes terribly expensive once you realize you need multiple accounts (not just aliases) for different people in the family. At least for me, paying a few hundred dollars on Fastmail (or anywhere else) for email is really way too expensive. I've also written to Fastmail asking for flexible pricing options, but they responded that they're not even considering any changes on pricing/flexibility for the near future.
Edit: If one doesn't need custom domains and office suites, I'd recommend only Posteo! That company is way ahead of others in being better for all humans (read on their website about all the things they do).