Sending, receiving, and organizing email in Outlook.com
None of the suggested measures I have seen helps. I removed quite a few entries in order to check if the lists had reached maximum size ... reducing the sizes of the lists DID NOT fix the issue with saving changes in the browser version
This bug, for most people, is a backend problem. i.e. It's not the size of your Safe/Blocked list or anything you can fix using an Outlook client. It's a problem with how Outlook interfaces to your mailbox on the Microsoft Mail Servers.
The only known fix is to bring in Microsoft Support:
- Logon to https://outlook.cloud.microsoft/
- From the main menu: Help -> ? Help
- {This should open the Help side panel}
- Search Help -> {Your problem} and press Enter
- Still need help? [Yes]
- If you get "We're here to help": Tell us your problem -> {Your problem, again} [Get Help]
- [Sign In] {Use any Outlook/Microsoft account}
- Choose a support option -> Chat with a support agent in your web browser
If you only need to get an email off your Blocked list, or add to Safe, but can't save changes:
Possible Workaround - Add to Contacts. See the Answer by "Hornblower409 Sep 5 2026" in
https://learn.microsoft.com/en-us/answers/questions/5989552/couldnt-save-changes-when-unblocking-an-email