GOOD NEWS EVERYONE - I've been in touch with Microsoft and they had the following to say:
Thank you for getting back to us. I would like to inform you that we have just received information that the request for setting the reading pane in light mode, permanently has been accepted and the feature is currently rolled out to Insider build. I would suggest to wait for this to be rolled out in Production build, as this is a stable build. Hence, we request to continue keeping Outlook updated to the latest build when available to avail the feature when released.
Once again, I thank you for your co-operation and understanding.
Email background in dark mode should be white, not black. Or at the very least we should have the option to permenantly set it.
Impossible to read bolds in white and emails look awful. Some will disagree but place an option to let users decide, don't force this on customers!
Thanks for the feedback! We are working on this.
Current Dark Mode support: https://docs.microsoft.com/en-us/officeupdates/release-notes-office-for-mac
We should be able to select the background colour and set default for all emails. Either dark or light as a global choice, not dictated by MS!