Allow the ability to select multiple messages when sorted by from without having to expand the list.
If you set the sort by from all the messages are listed unexpanded from each sender. If select the sender you are not able to do any actions (delete / move / archive) you have to expand each sender first and then manually select each message. It means it takes a huge amount of time if you have select 500+ messages from one sender. On PC Outlook you can select all messages from multiple senders very easily.
I and my staff have lost many hours of productivity when cleaning up mailboxes due to this functionality missing.