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.

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.

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

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.

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

I want to be able to pass the contents of mail messages in a certain folder to a script. I control the script so I can handle them how ever you want to pass them. File handle, stdin, command line option, etc.

Even the option to store that folder in MBOX format so that I could just tail -f the tile would work.

When I paste into an email I usually want to keep the formatting of the email, not the one from the copied source. However, the default paste option is 'Keep source formatting' and cannot be changed, so I need to paste, click on the clipboard icon, select 'Match destination formatting' which is cumbersome.
This is an available configuration option in the Windows version.

Add a "Send Sent Item To" button in Outlook for Mac

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.

Please add the option to permanently delete emails without confirming

It is way too easy to "un-Star" a favorite.
please make me confirm that I meant to un-star a favorite.

Currently I create rules on the computer that I'm working on but these do not sync between multiple machines. Being able to either add to iCloud and sync with all accounts or even just export the rules to manually add would help

Inline mini translator for Office 365 for Mac. Similar to what you have for the windows version.
The ability to select text in the mail and a hover box appears with the translated text.
I am English speaking living in Germany so this is vital to my productivity.

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.

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.

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.