I'd recommend Posteo [1] and Mailbox [2] to people mainly for the costs. They're cheap and are a lot more flexible in pricing as your needs grow.
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).