Not related to the article but the show stopper for me trying to install/test this email reader is that it won't work with just a generic IMAP server. I've got to be using Outlook or Office365 or whatever.
You're right. It is unusual. We went with Exchange Web Services first instead of IMAP. Our initial target market were larger companies and we wanted to have deep integration with their Exchange servers (Calendars, Contacts, etc).