If you need for example -->> All mail sent to sally@contoso.com and info@contoso.com will go to Sally's Inbox then follow below given steps -
Sign in with your Office 365 admin account on the Microsoft 365 admin center.
Select Users.
On the Active users page, choose the user.
Next to User name / Email, choose Edit.
Important: If you've just created or licensed this user, you can't add an email alias until the user's email is fully provisioned. It can take up to 30 minutes.
On the Edit email addresses page, in the text box under Alias, type the first part of the new email alias. If you added your own domain to Office 365, you can choose the domain for the new email alias by using the drop-down list. Then choose Add.
Note: The email alias must end with a domain from the drop-down list. To add another domain name to the list, see Adding additional domains to Office 365.
When you're done, choose Save.
Wait 24 hours for the new aliases to populate throughout Office 365.
The user now has a primary address and an alias. All mail sent to sally@contoso.com and info@contoso.com will go to Sally's Inbox.
Sign in with your Office 365 admin account on the Microsoft 365 admin center.
Select Users.
On the Active users page, choose the user.
Next to User name / Email, choose Edit.
Important: If you've just created or licensed this user, you can't add an email alias until the user's email is fully provisioned. It can take up to 30 minutes.
On the Edit email addresses page, in the text box under Alias, type the first part of the new email alias. If you added your own domain to Office 365, you can choose the domain for the new email alias by using the drop-down list. Then choose Add.
Note: The email alias must end with a domain from the drop-down list. To add another domain name to the list, see Adding additional domains to Office 365.
When you're done, choose Save.
Wait 24 hours for the new aliases to populate throughout Office 365.
The user now has a primary address and an alias. All mail sent to sally@contoso.com and info@contoso.com will go to Sally's Inbox.
Refer link - https://docs.microsoft.com/en-us/office365/admin/email/add-another-email-alias-for-a-user?view=o365-worldwide
https://blogs.technet.microsoft.com/hot/2012/04/26/how-to-add-an-alias-to-an-office-365-account-and-how-to-set-up-outlook-to-send-email-messages-as-this-alias/
https://support.office.com/en-us/article/add-or-remove-a-user-s-email-alias-cb86b53b-bebf-4e0a-b781-c49270d85ea3
Was this article helpful?
That’s Great!
Thank you for your feedback
Sorry! We couldn't be helpful
Thank you for your feedback
Feedback sent
We appreciate your effort and will try to fix the article