Configuring preferences and options in Outlook.com
Hi Erik Grant,
I'm sorry you're running into this issue, and I understand how frustrating it can be when Outlook won't save changes you've made.
Based on your description, especially since you've already tested different devices and browsers, this may be a temporary server-side issue affecting Outlook.com rather than a problem with your local setup. Microsoft periodically investigates and resolves service-related issues of this nature, and in some cases the problem is resolved automatically once backend fixes are deployed.
For now, I recommend waiting a day or two and then trying again to see if the Safe Senders list can be saved successfully. In the meantime, you can monitor Microsoft's cloud service status for any reported service disruptions or incidents here: https://status.cloud.microsoft/
Thank you for your patience and understanding. Hopefully the issue will be resolved shortly, but if it continues after a couple of days, please let us know and we'll look into additional troubleshooting steps.