Seconding this - reasonable pricing and I haven't had any issues at all with the service. I haven't used FastMail but most things I read suggest they are very similar in terms of what they offer so I would think Mailbox is a good EU alternative for someone who likes FastMail. (There are also other EU providers like Tuta but with slightly different trade-offs, ie, more emphasis on privacy but at the expense of IMAP/SMTP support.)

I switched to mailbox recently and I'm finding it quite good. I set it up with a custom domain, and that did require a bit of fuzting around, but the friction there was almost all on the side of my VPS hosting service, not Mailbox's fault.