Comment by andros

GUIs cannot be built either before or during the specification of a protocol. In fact, this is the part that should have the least weight. There are important steps, such as system auditing or making design decisions (like certificate rotation), that are not addressed. However, the goal is not to replace SMTP/IMAP, but rather to show how modern tools, when properly assembled, can replace older protocols with serious design flaws. JMAP is flexible, mature, and easy to connect with current technologies. It's a better option.