License & Subscription Issues

How to Fix Outlook Mailbox Still Full After Updating OneDrive Storage

Maira Mehtab Sep 22, 2026 868 views

Question details

The user has upgraded their Microsoft storage (e.g., adding 100 GB to OneDrive) but their Outlook mailbox still shows that it is full (stuck at the 5 GB basic limit), preventing them from sending or receiving emails.

Product: Microsoft Outlook
Device & OS: not provided
Scenario: Checking and managing email storage quotas after purchasing an additional Microsoft storage subscription.
Observed behavior: The newly purchased storage applies successfully to OneDrive, but the Outlook mailbox quota remains unchanged and full because the two storage limits are tracked separately.

Before you start

Verify that you are logged into the correct Microsoft account associated with the storage upgrade, and keep in mind that it can occasionally take 24 to 48 hours for storage quota changes to synchronize across all Microsoft services.

Solution 1Recommended

Clear Space Using the Outlook Storage Management Tool

Because OneDrive and Outlook maintain separate storage limits, you must directly manage and free up your mailbox space regardless of your OneDrive capacity.

Microsoft separates cloud file storage (OneDrive) from email storage (Outlook). Purchasing a basic OneDrive storage expansion often does not automatically expand your Outlook mailbox size.

To resolve the "mailbox full" error immediately, you must identify and remove large attachments and unnecessary emails directly from your Outlook account settings.

Access Microsoft Storage Settings

Sign in to your Microsoft account online. Click on the gear icon to open Settings, then navigate to Account > Storage to view a breakdown of both your email and cloud storage usage.

Open Outlook Storage Manager

In the storage settings or directly within Outlook on the web, click on "Manage Storage" under the Email storage section.

Delete Large Items

Sort your emails by size and permanently delete messages containing large attachments, old newsletters, and unneeded files.

Empty the Deleted Items Folder

Navigate to your "Deleted Items" and "Junk Email" folders, select all items, and permanently delete them to ensure the storage space is actually freed up.

Subscription Quotas: If you purchased a Microsoft 365 subscription (like Personal or Family) that explicitly includes 50 GB of Outlook storage but it still shows 5 GB, your account may be experiencing a synchronization issue.

Solution 2

Contact Microsoft Support for Sync Issues

If you have verified that your specific subscription plan includes expanded Outlook mailbox storage but the quota remains full after 72 hours, you need backend support.

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Frequently Asked Questions

Why didn't my Outlook storage increase when I bought more OneDrive space?

Microsoft manages cloud file storage (OneDrive) and email storage (Outlook) independently. Unless your specific subscription plan explicitly includes an Outlook mailbox expansion (like Microsoft 365 Basic, Personal, or Family), buying a standalone OneDrive storage add-on will only give you space for files, leaving your email quota at the free 5 GB limit.

How long does it take for a Microsoft storage upgrade to activate?

It typically takes anywhere from 2 to 24 hours for a newly purchased storage subscription to reflect on your account. In rare cases, it can take up to 48 hours for the new quota to synchronize with your Outlook mailbox.

What is taking up all the space in my Outlook mailbox?

The most common culprits for a full mailbox are emails with large file attachments (like PDFs, images, or videos), inline images in long email threads, and accumulating messages in the Deleted Items and Junk folders.

Can I merge my OneDrive and Outlook storage quotas?

No, Microsoft does not allow users to pool or merge their storage quotas. The 50 GB limit for Outlook and the storage limit for OneDrive are strictly segregated, even though Outlook attachments may utilize OneDrive space in certain sharing scenarios.

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