There are several Ask HN posts about alternatives for Gmail. Apart from Fastmail, there are more privacy focused services. Some of them: posteo.de, runbox.com,

There are several Ask HN posts about alternatives for Gmail. Apart from Fastmail, there are more privacy focused services. Some of them: posteo.de, runbox.com, mailbox.org and mailfence.com. These are a lot cheaper than Fastmail too, with full IMAP support. If you want a much cheaper service for many mailboxes, take a look at Migadu. For most people who need multiple mailboxes but don't send a lot of emails (but receive many), I'd find it hard to beat that pricing.