how to unstack emails. they are stacking under one email and I want to turn it off

In Outlook, stacked emails are usually “conversation” or “threaded” view. To turn this off in Outlook mobile (iOS/Android):

1. Open Outlook and, from the message list, tap the mail icon in the upper-right corner to open the folder pane.
2. Tap Settings.
3. Under General, tap Mail.
4. Tap Email Organization under the Inbox section.
5. Toggle Group emails by conversation to Off.

Messages will then appear as individual emails instead of being stacked.

References:

• How do I disable threaded or conversation mode?