Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello Mathew,
If you mean that you want to use the alias to sign in Office 365 portal, it is not feasible to meet your requirements. The alias is only used to receive emails in Office 365 for Business. Please use the primary email address to sign in. I suggest you create a new vote in the UserVoice forum for feedback: https://office365.uservoice.com/
Thanks for your understanding and cooperation.
Regards,
Rick