Addendum: Replicating Hey.com Features in MailMate
To do this I created a new Smart Mailbox with the following mailbox filtering criteria:
Furthermore, in the same mailbox configuration window, but under the ‘Submailboxes’ tab be sure to select the checkbox to create submailboxes, and choose an appropriate filter. For creating People Pages, I went with the ‘From | Name’ option.
My thanks to Martin for drawing this omission to my attention, and I hope this helps others.