The framework for legally deploying and using Microsoft Exchange Server or Exchange Online, based on server and client access models.
In the Microsoft 365 admin center, the message “This user doesn't have an Exchange Online license” in the mail section means that no Exchange Online–enabled product license is assigned to those users. Without an Exchange Online license, a user mailbox is not created or usable in Exchange Online.
To fix this for users who should have mailboxes:
- Go to the Microsoft 365 admin center → Users → Active users.
- Select a user who should have email.
- In the user details, check Product licenses and confirm that a plan including Exchange Online (for example, an Office 365 Enterprise plan) is assigned.
- If no such license is assigned, edit the product licenses and assign one that includes Exchange Online.
- Repeat for each user who needs a mailbox.
After assigning a license, mailbox provisioning can take up to about 15 minutes, and in some cases up to 24 hours before everything is fully available. If a user previously had a license that was removed, the mailbox can be reconnected only if the license is reassigned within 30 days of removal; after that, the mailbox is permanently deleted and cannot be recovered.
If the purpose of an address is only to function as a queue or shared mailbox, consider using a shared mailbox instead, which does not require an Exchange Online license.
If licenses are correctly assigned and the mail section still shows no Exchange Online license after 24 hours, contact Microsoft Support via the Microsoft 365 admin center so they can check the tenant and mailbox provisioning.
References:
- Fix NDR error "550 5.1.10" in Exchange Online
- "Email can't be received because the license is invalid for the mailbox" error when selecting Test & Enable Mailbox
- You can't find a user in the offline address book in Microsoft 365
- Delays in provisioning of user/mailbox or synchronizing changes in Exchange Online
- Can't access the mailbox of an unlicensed user in Exchange Online
- Manage mail users in Exchange Online