Dear Art,
The onmicrosoft.com address is created automatically for every Microsoft 365 account and can't be removed. You can add your own domain and make it your main address, and the onmicrosoft.com address will stay in the background as an alias. First, you must own LeadershipInitiativesGroup.com and have access to its DNS settings.
- Sign in to the Microsoft 365 admin center.
- Go to Settings > Domains > Add domain.
- Enter
LeadershipInitiativesGroup.com.
- Add the TXT record provided by Microsoft at your domain registrar to verify ownership.
- Add the required Microsoft 365 mail records, including MX, SPF, and Autodiscover.
- Go to Users > Active users, select your account, and change the primary username/email address to:
yourname @LeadershipInitiativesGroup.com
- Make sure the account has a license that includes Exchange Online.
After DNS propagation, messages sent from the business mailbox should show the custom address.
For reference: Add a Custom Domain to Microsoft 365 - Microsoft 365 admin | Microsoft Learn
Forwarding to outside addresses is blocked by default for security, so you'll need to allow it first:
In the Microsoft Defender portal, go to Email & collaboration > Policies & rules > Threat policies > Anti-spam, open the outbound spam policy and set automatic forwarding to On. Then go to Microsoft 365 admin center:
- Select Users > Active users.
- Select the business account.
- Open Mail > Manage email forwarding.
- Enable forwarding and enter the external address.
- Select Keep a copy of forwarded email in this mailbox.
- Save the change.
The admin center only supports one address, so to forward to both, create an inbox rule in Outlook on the web under Settings > Mail > Rules that forwards all incoming messages to both personal addresses.
For reference:
All you need to know about automatic email forwarding in Exchange Online | Microsoft Community Hub
Configure email forwarding - Microsoft 365 admin | Microsoft Learn
I hope this helps. Looking forward to your reply.
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