I’m not sure that I ever knew the Home/Family version of Microsoft 365 supported custom domain names. I was changing some settings in Outlook and ran into a notification. It was a warning that the ability to add custom domain name to your Priemium Microsoft account would expire on November 30th of 2023. Not one to miss out on features I am paying for, I decided to dig a little deeper. You can review the notification message yourself here. https://support.microsoft.com/en-us/office/changes-to-microsoft-365-email-features-and-storage-e888d746-61e5-49e3-9bd1-94b88e9be988
If you reading about this feature for the first time like I did, here’s what to know. If you have, or are willing to buy, a custom domain name from GoDaddy.com you can use it for email with your Microsoft 365 subscription. According to the official instructions, public DNS records for the domain must be hosted with GoDaddy.
I already had a domain name from GoDaddy and was able to use it without issue. The process was more complicated than it would have been if had I purchased a brand new domain name from GoDaddy through Outlook. I had to manipulate DNS records manually to make my domain work. It is my understanding that part of the process is automated if you purchase the name though Outlook.com.
Whether you already own a domain or are purchasing one, the setup starts with logging into what is commonly called OWA (Outlook Web Access) aka your Outlook.com account https://outlook.live.com will get you there.
Click on the Gear icon (settings) in the upper right hand corner.

In the pane that opens click View all Outlook Settings at the bottom.

Now click Premium, then Personalized email address.

You can read the notification, use the Manage button to sign-in to your GoDaddy account, or set one up if you don’t already have it. Microsoft’s own documentation on the setup, questions, and troubleshooting is where you should turn for the rest of the configuration. They’ve made the process fairly simple, it took me about forty-five minutes to get my custom email addresses fully working on the Internet. If you complete the setup process before the deadline, your custom email address will not stop working.