What's the difference between regular email and forwarding email addresses?
Regular email addresses and forwarding email addresses are two different address types used to deliver email.
A regular email address has its own, unique inbox where you can send, receive, and access your email. You can access your inbox online or with an email client (like Outlook or the Mail app).
A forwarding email address automatically directs incoming messages to another email address. You'll then access your email using the other account's inbox. For example, you can create a forwarding address to automatically deliver mail sent to your professional email account to your personal email account.
With Microsoft 365, if you choose, you can keep copies of forwarded messages in the original inbox so they can be accessed from both accounts. Otherwise, the same email address can't be both a regular email address and a forwarding email address. If you change your mind, you can delete the forward so it's set up as a regular email address.