email storage full

Hi @Garry Kichin,

Welcome to the Microsoft Q&A forum.

I would like to provide you with the following information:

When you subscribe to a Microsoft 365 Business plan, you receive 2 TB of storage. However, this 2 TB is allocated to OneDrive for storing all files, not to Outlook.

For Outlook (mailbox), the default storage quota is 50 GB. To extend your email storage capacity, you can enable Online Archive (In-Place Archive). Once this feature is enabled, your mailbox storage will be expanded by an additional 50 GB for the archive mailbox.

You may refer to the following document for more details:

Exchange Online limits - Service Descriptions | Microsoft Learn

You can enable this feature by following the steps below:

Step 1: Access the Exchange Admin Center

Step 2: Select Recipients > Mailboxes, then locate and select your mailbox

Step 3: Select Other > Manage mailbox archive and enable Archive

After completing these steps, an additional Archive mailbox will appear in Outlook, as shown in the illustration.

At this point, older emails (for example, emails from several years ago) will be automatically moved to the Archive mailbox based on the retention policy. Additionally, you can also move emails manually by following these steps:

• Press Ctrl + A to select all emails
• Select Move > Select a difference folder > In-Place Archive

The selected emails will then be moved to the archive mailbox.

 I hope this information is helpful. Please follow these steps and let me know if it works for you. If not, we can work together to resolve this.   

Thank you for your patience and your understanding. If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.

I look forward to continuing the conversation.

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For a Microsoft 365 business (work/school) account, the 2 TB (or 1 TB) OneDrive storage does not increase the mailbox size in Outlook. Mailbox storage and OneDrive storage are separate.

For business mailboxes in Exchange Online, the mailbox limit is typically up to 100 GB, and administrators can configure smaller limits such as 50 GB. When the configured mailbox quota is reached, sending and receiving email stops and a “Quota Exceeded” / “mailbox is full” message appears.

To fix this without deleting mail, an administrator must change the mailbox size limits in Exchange Online; end users cannot override this themselves.

Steps for an admin (work/school account only):

1. Go to the Microsoft 365 Admin Center and open the Exchange Admin Center.
2. Navigate to Recipients > Mailboxes and select the affected mailbox.
3. Open Mail flow settings > Message size restrictions and review the mailbox storage configuration (the article notes that mailbox storage can be set per user or globally).
4. Adjust the mailbox size/quota according to the organization’s policy, up to the service limit (commonly 100 GB for Exchange Online mailboxes), and save.

If increasing the mailbox quota is not allowed by organizational policy, the only supported way to get back under quota is to reduce mailbox size (for example, by moving mail to an archive mailbox if enabled, exporting to a .pst, or permanently deleting items). The OneDrive 2 TB cannot be used directly as extra mailbox storage.

To see and manage mailbox usage from Outlook on the web or the new Outlook client:

• New Outlook for Windows: Settings > Accounts > Storage to view folder sizes and use Clean up Mailbox options.
• Outlook on the web: Settings > Account > Storage to view usage and clean up.

If self-service options are insufficient and mailbox quota remains at 50 GB, contact the organization’s IT administrator to:

• Confirm the current mailbox quota setting for the account.
• Increase it (up to the Exchange Online limit) if permitted.
• Optionally enable an Online Archive mailbox to offload older mail without deleting it.

References:

• Mailbox storage limits in Outlook