Date Separator in Inbox
One of the few things I like about Outlook Mac is in the inbox there is a separator line to organize each day. So you have your messages from today with a separator bar underneath "Today", same for "yesterday", then "Tues", etc.

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chehab commented
as @AL, this one is a must have, with exact date on the separator like in "Mail Pilot".
http://mindsense.co/mailpilot/.resources/images-2/reminders-bg.jpg -
AL commented
This, to me, is the only seriously important option missing from Airmail2. It's what makes me have to use Outlook because there is too much clutter in my inbox otherwise. Serious bummer that it isn't a feature. And, date filter simply isn't a replacement for this feature.