Though that makes it sound like it would work with any email provider. It's not clear that JMAP is a protocol. "Building a JMAP email client in half an hour"?
Maybe there's not enough interest in JMAP yet, and a talk that promotes JMAP over IMAP/SMTP would be better first. Maybe the client could be prebuilt and simply presented as part of the talk as FOSS, showing the small LoC that it took and simply mentioning how little time it took. Maybe having it in multiple programming languages would help, too, to show that its simplicity is not a matter of language of choice.
Just throwing ideas out there.