Here’s some information from Microsoft about making emails accessible in the Outlook client:
There is a lot of common sense stuff in that article, but one thing I didn’t realize: in dark mode, you’ll want to go and double check the accessibility checker pane, because errors don’t automatically show up.
There’s also a way to request accessible emails from senders, but to do so, you need Windows, and Outlook will send you to the web version of Outlook. It’s not available in the Mac or iOS versions. Normally it’s the desktop client that has all the hidden settings. 🤷🏻♂️