Using New Outlook on Windows for personal email, calendar, and contact management
Hi @Anne Mc
I understand the frustration. A Microsoft 365 Personal subscription does not provide the Exchange Admin Center or business mailbox controls, so the administrator instructions you found do not apply here.
Selecting an alias in the From field changes the sending address, but it does not create a separate display name for that alias. The name shown to recipients is taken from the account or mail provider’s sender information. New Outlook currently does not provide a setting to assign a different display name to each alias.
You can try changing the name on your Microsoft account profile, but that change applies to the account generally, not only to the alias. Also test sending from Outlook on the web. Outlook.com officially supports choosing a Microsoft account alias through Options > Show From, while the desktop app may handle aliases differently. Send email from a different address in Outlook.com
If domain.co.uk is hosted by another email provider, the sender display name may need to be changed with that provider instead. In that case, please let us know who hosts the mailbox and whether the account was added to Outlook as IMAP or as an Outlook.com account.
Hope this helps