Hi Christine, this is Bryll
Thank you for taking the time to write us in the Microsoft Community.
According to your post, it sounds like you are trying to add Dy******@outlook in New Outlook for Windows along with your main account ch******@outlook.com.
If our summary is correct, can you confirm if Dy******@outlook is an Alias email address of ch******@outlook.com? To check, please login here Add an alias (live.com) If Dy******@outlook is an Alias email address of ch******@outlook.com, it means that they are both linked to the same account and share the same inbox, contact list, and account settings. Outlook.com allows you to have multiple aliases associated with one account, but New Outlook does not allow aliases to have separate mailboxes as they all use the same inbox or email server.
Also, are you able to add both Dy******@outlook and ch******@outlook.com on a different mail program like Mozilla Thunderbird mail? You can download Mozilla Thunderbird in Microsoft Store to try.
While we wait for your response, these are the nearest tactics that correspond with the described problem:
Restart New Outlook:
- Right-click Windows Start menu and select Task Manager.
- Go to Details tab and Find Microsoft Outlook, then End task.
- Check to make sure that new Outlook is closed, then close Task Manager.
Uninstall and reinstall the new Outlook for Windows:
- From the Start menu, select new Outlook for Windows.
- Select the arrow to expand the list option in Start.
- Select Uninstall to begin the uninstall process.
To reinstall new Outlook:
- Open classic Outlook for Windows.
- In the top corner, you'll see a toggle to Try the new Outlook

- Select this toggle to download the new app and you will switch to the new Outlook for Windows.
If needed, you can refer to this link to go back to Classic Outlook for Windows then re-add your email accounts and once they are all added, you can then toggle back to the New Outlook for Windows: To learn how to toggle out of New Outlook, click here: Toggling out of the new Outlook for Windows preview - Microsoft Support
We will recommend other strategies once we receive your response to our questions outlined above. If possible, please share some screenshots or video of the problem.
Best regards,
Bryll
Community Moderator