One of the common requirements in administering Exchange Online is monitoring and restricting mailbox sizes to ensure only the required resources and licenses are used. However, as communication needs expand and data volumes grow, there may arise a requirement to extend mailbox sizes for some users. You can do this by applying a different license to the user to increase their base storage or remove any limitations like their Prohibit Send and Receive quota.
ManageEngine M365 Manager Plus, an extensive tool used for reporting, managing, monitoring, auditing, and creating alerts for critical activities in your Microsoft 365 environments, can be used to carry out both of these actions in just a few clicks.
Applying a different license to increase Exchange Online mailbox sizes
- Log in to M365 Manager Plus and navigate to Management > Azure Active Directory > License Management and select License Modification.

- Select Modify Selected Licenses in the Assign/remove licenses drop-down.
- Click the Select Licenses field, expand the Exchange Online subscription that you want to apply, and check Exchange Online. Click OK to confirm your selection.

- Select your Microsoft 365 Tenant from the drop-down, type in the list of users for which you want to increase the mailbox sizes, and click Find.

- You can also modify mailbox sizes for users in bulk. Select CSV Import, click Browse to upload a CSV file with the users for which you want to increase the mailbox sizes, and click Import Users.

- The users selected will now have the new Exchange Online licenses assigned to them, which will increase their base mailbox size.
Modifying the message quota to remove size restrictions
- Log in to M365 Manager Plus and navigate to Management > Exchange Online > Mailbox Management and select Set Mailbox Storage Limit.

- Check Prohibit Send and Receive Limit and enter the new limit in the adjacent fields.
- Select your Microsoft 365 Tenant from the drop-down, type in the list of users for which you want to increase the mailbox sizes, and click Find.

- You can also modify this limit for users in bulk. Select CSV Import and click Browse to upload a CSV file with the users for which you want to increase the mailbox sizes, and click Import Users.

- The users selected will now have the new Prohibit Send and Receive limits assigned to them, which will let them use more of their mailbox storage.
Highlights of M365 Manager Plus
- Bulk management: Manage mailboxes, users, sites, groups, and contacts effortlessly in bulk.
- Extensive reports: Gain a thorough understanding of your environment in Exchange Online, Azure Active Directory, SharePoint Online, OneDrive for Business, and other Microsoft 365 services with detailed reports.
- Comprehensive auditing: Keep tabs on the most granular user activities in your Microsoft 365 environment.
- Real-time notifications: Receive instant email notifications about critical activities.
- Constant monitoring: Monitor the health and performance of Microsoft 365 features and endpoints around the clock.
- Customizable help desk roles: Create custom roles with any combination of reporting, management, and auditing tasks. Assign these roles to non-administrative users to reduce the workload of Microsoft 365 admins.
To learn more tips and tricks that can simplify your Microsoft 365 tasks, click here.