I agree the arrows do disappear at times, and the Always use Outlook service for images is safer. I am able to get the arrows back for a long session by setting back to Do not use Outlook and saving; then reset back to Always use Outlook and saving again. I know this is a temporary fix until Microsoft updates. I am wondering if Microsoft is insisting users of Outlook must install Office to get it all Outlook options? Is there a free version of Office?
I've set up Mozilla Thunderbird to work with it before, but ran into an issue where it would download all of my e-mails from scratch every few months, so I scrapped that. I've never used the Windows 10 Mail app, but Microsoft has a new "One Outlook" app in the works for Windows 10/11. It's apparently identical to the Outlook Web -- so they'll still need to fix this issue, lol.