Well, based solely upon the number of times JMAP is mentioned in TFA, I'd guess it's because Fastmail is likely the only(?) provider who uses it I _suspect_ th

Well, based solely upon the number of times JMAP is mentioned in TFA, I'd guess it's because Fastmail is likely the only(?) provider who uses it I _suspect_ this is whatever the marketing equivalent of a "backronym" is: in that they decided to partner with Fastmail, then Fastmail was all "JMAP or GTFO", and then a blog post resulted talking about how awesome JMAP is