Allow Office for Mac users to set the default meeting duration to end early, i.e. 25 min for 30 minute meetings and 10 minutes less for 1+ hour meetings.

This feature is already supported on Windows client and on GSuite.

Move search bar within Outlook back to its old location. The new location of the search bar is inconvenient and not intuitive, the search field should be closer to the emails themselves instead of excommunicated to the blue bar at the top of the netherworld. Not sure why anyone thought that would be a good idea or that anyone would have asked for that. Please move it back within the body of Outlook so it is closer to the email content that needs to be searched.

Make the new Outlook available to users of Exchange OnPremise again. Or at least: let us know whether it will ever come back or not. I used to work with it just fine (fast insider), and then suddenly the support stopped, with no explanation whatsoever.

It should be extremely obvious to the user when a message was not sent for some reason (attachment size, etc)–not just by the number of messages indicated in "Outbox". This directly impacts the reliability of the service and my reputation as a business owner.

Ability to export signatures or have the signatures centrally stored in 365 cloud. This is really quite necessary for migrating users between machines. @LukeHamburg has summed it up perfectly here:
https://answers.microsoft.com/en-us/msoffice/forum/msofficeoutlook-msomac-mso_o365b/outlook-2016-mac-signatures-how-to-export-import/1bfa4b27-4ea4-46c1-8263-c92ae557b277

You have the option to recur monthly on the first, second, third, fourth and last [Monday, Tuesday, etc.], but some months have 5 Monday, Tuesday, etc. Selecting last may put it on the 4th which may not be correct. I use the outlook calendar for my boss so they have access to their schedules from their phones when there aren't near a computer.

whenever I add an (inline) image to a message, outlook automatically generates Alt Text to helpfully describe this graphic. please provide a way to disable this. I share design visuals many times a day, and this description is almost never even close: eg a recent effort was tagged as being 'A parrot'. which it really wasnt

Separate the calendar function into a separate app so we can see our calendar side by side with our email, or just open one or the other. Often, I want my calendar open but not my email to minimize distractions.

We use encryption regularly. Outlook regularly crashes when trying to open an attachment in an encrypted email. Sometimes I will have to try to open the attachment 3 or 4 times before I'm successful (with Outlook crashing each unsuccessful attempt). If I have any draft emails that have not been sent when Outlook crashes, they are often not autosaved. Please make Outlook more robust with encrypted email.

I occasionally receive emails related to production support tasks which must be acted on immediately. I'd like to be able to create a rule to play a custom sound when I receive one of these emails.

Since I can use rules to mark them high priority, another option is just having a different sound for high priority emails.

It would also be nice to have an option to always play this kind of sound over my system speakers. That way if I'm not wearing my headphones or I step away, I can still be alerted.

When I create a new folder/sub-folder, it immediately takes me to that folder immediately after creation. I usually am creating a folder to move messages into that folder. If I am immediately taken to that folder, I have to go back to the original folder, select the messages, then drag/drop them. It's pretty useless to go to an empty folder.

I would like to be able to add a room onto a meeting that was created by someone else. It would be useful when a client invite us at a meeting and we have to regroup in a meeting room.

Show Unread Message count next to Smart Folders, the same way it shows up for all other folders. The use case here is that I've created smart folders for mail in my Inbox that is from key people (one smart folder per person) that I need to prioritize. When new mail arrives from one of those people, I need a visual queue that a new message has arrived from that person.

The calendar should appear so you can quickly choose a date, rather than scrolling up and down on days and months. Same for the time... Suggest 09:00, 09:30, 10:00. 10:30 etc.

I have two companies I’m working for and often when I’m writing a new email, it is being sent from the wrong domain and i accidentally send emails meant for coworkers at one domain from the domain of a different company. It’s dangerous. I'd like to separate address books so when I’m writing an email from domain X, it doesn’t pull up the addresses associated with domain Y. In a hurry I'll make the mistake and the damage is done.

Allow the "Move To" folder picklist to be longer than 10 folders.

Like windows we need to option to view the OLM files , In windows it can be done just using the Outlook menu : File ->open and export -> Open outlook data files (.pst)

Exchange has a feature called Message classification which displays a classification on an email in Outlook. This function works properly on Outlook on Windows, but does not function on Outlook on Mac.