Only real alternative is PurelyMail, which is ok for the simplest cases. Beyond that, their "advanced pricing" is unnecessarily complex and FranklyMail seems to be more polished overall.
Other providers want $5/month per account, which is insane if all you need is e-mail.
The no per-seat pricing is a refreshing approach for email hosting. I upvoted this. Supporting JMAP alongside IMAP and SMTP is also a nice touch for keeping things flexible.