Show meeting participants' email addresses as a tooltip in the Scheduling view.
When you are invited to a meeting, the only way to get to the email addresses of the other participants is to use the Reply All button. You should be able to access the contact card (or at least see the email address) by hovering over the attendees in the Scheduling view.
This is an annoyance literally every day at work for me. Just to check and see whether other attendees for a meeting are internal or external, I have to open the scheduled meeting, switch to the "Scheduling" tab in the ribbon, click Reply All, then double-click each individual contact, then close the email, and finally Discard All Changes.
SUCH a waste of time!
Terry Jones commented
YES! It would also be useful to show which contacts are internal and which are external on the attendee list.