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

Hi, I just encountered a problem in the new Outlook Calendar design (black). If one wish to insert an appointment with yellow background, the text in it remains white. It is hardly to read. It would be much more convenient, if it changed automatically to black or any darker colour.

Microsoft tech support should not send the user to users groups for answers. Microsoft ought to support its own software!

Give me an option to disable the contact names popup when I type @something. I don't want to insert an email address, I want an at-sign (@) in front of a word. For example, @somewhere.

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.

Currently the Address Book in Outlook for the Mac is not able to show all Address Lists on the Exchange server or in Exchange Online.
If you create a custom address list in Exchange it does not show up in Outlook for Mac.
In Outlook for Windows or even in Outlook on the Web you can see custom Address Lists or even more default Address List on the Exchange Server.

Using Outlook under different operating systems is cumbersome as there is no feature parity among the different clients.

There is a feature in the outlook for windows application (when you press esc it closes the message that is on the screen), but this functionality is not in outlook for macOS. It would be more practical if you had this option in Mac outlook

Pleas implement the bulk edit of categories for all objects (contacts, notes, appointments, mails, etc.)

I need to change categories in my contacts database and can do it only for single entries, that's a nightmare because I have a huge contact database.

In the new version of Outlook for Mac, the conversation view is too hard to follow when multiple "active" emails are in my inbox. The mix of archived emails, sent emails and more makes the email chain crazy to follow. Please add the option to hide emails not in the current folder (i.e. when I'm in the Inbox View, I see all items in the conversation that are also in the inbox). Then like in the old version of Outlook, you can have the button to show all.

It seems like a pretty good idea during a global pandemic when everyone is online chatting in meetings all-day. Instead of finding where my cursor is on my screen, maneuvering it to the tiny mic icon to unmute myself, I could simply use a hotkey combo to do it for me, like Slack and Zoom. Microsoft is so frustrating.

I used to have the excellent option to double-click an email and open it in a pop-up window. This helps to keep an email open while browsing throuhgh inbox for information that I could cut/paste into the new email. I am not able to do this currently on 365 for Mac because I completely LOSE the inbox-view when in a new message is open. I am sure this is a simple fix that would help me and my research community who have recently migrated to 365 and who have noticed this crucial oversight.

Enterprise macs who uses office365 mostly uses autodiscover.domain.com as the way to setup things. However MS Outlook for mac goes first to try domain.com then autodiscovery.domain.com. This way it creates unwanted traffic on your company's website. If you have quite many macs you get much unwanted traffic.

Outlook has the function "Archive".

Unfortunately, this is only possible for mails you receive. (Inbox)
Why isn't this for sent mail? (Outbox) I don't understand!
What does that make sense just to archive the receipt and not send mails.
Only half of it is archived!
Is then again to search/find in two different places

Archiving should also be available for sent mails!

Run an AI to combine or suggest the user of uservoice.com to combine while trying to write an existing suggested idea, to not let the users keep on repeating the same.

Make the full conversation viewable in tasks, even the emails sent and received after creating the task, will greatly help on tracking it.

My Outlook for Mac Office 2011 has stopped working, please help as not received emails since 5th May 2020?

Please include a rule for the mail filter "DOES NOT CONTAIN" a word inside the message body for example.

Right now I can only specify "DOES CONTAIN" in MS Outlook 16 for MAC

When my bank sends a 6 digit two factor authentication code, MacOS will suggest the code as an autofill on the banking screen. When Microsoft send 6 digit 2FA codes to access our corporate enterprise site, they don't get suggested as an autofill. When I change my corporate password (every few months) I can get up to 20 SMS messages with codes. Would be useful if I didn't need to type them all in across Mac Mail and all the MS office apps.