I'm a Fastmail customer, and speaking to them for my last startup, they were adamant that we couldn't use them for sending transactional emails to our customers. So I'm a bit confused why they're letting 1Password do this.
Are we allowed to use JMAP for sending transactional emails via Fastmail now? If not, then JMAP seems to be just a method for creating new Fastmail email clients, because no-one else supports it and Fastmail doesn't allow anything but conventional end-user activity.
Or is this wrong?
If I wanted to use JMAP for my next startup, is there a transactional email provider who supports it?
There's software like https://github.com/jmapio/jmap-perl you can use in front of your chosen provider but that seems like more headache than it's worth unless your imap implementation/lib is incredibly complicated.
Doing something like this is essentially a bet that your provider will eventually implement jmap.