Outlook Login Problems

Fix Outlook Sign-In Error Because Mailbox Is Full

Natalie Taylor Sep 27, 2026 869 views

Question details

The user is unable to sign in to Outlook because the mailbox storage has exceeded its maximum capacity.

How to Fix Outlook Sign-In Errors When Your Mailbox Is Full

Product: Microsoft Outlook
Device & OS: not provided
Scenario: Attempting to access Outlook on the web when the mailbox storage quota has been reached.
Observed behavior: Outlook blocks access and displays a QuotaExceededException error on the login screen.

Before you start

Ensure you have an active internet connection and, if you are on a corporate network, have your Microsoft 365 IT administrator's contact information ready.

Solution 1Recommended

Use Private Browsing or a Different Browser

Bypassing stored cookies and cache using private mode can sometimes grant temporary access to delete emails.

When Outlook encounters a storage error, your browser might cache the error loop. Opening a private browsing window ignores the current cache, which may allow you to sign in and clean up your inbox.

Open a Private Window

Open your web browser and press Ctrl+Shift+N (Chrome/Edge) or Ctrl+Shift+P (Firefox) to open a private or incognito window.

Sign in to Outlook

Navigate to the Outlook web portal and enter your credentials to attempt a sign-in.

Delete Unnecessary Emails

If you successfully bypass the error, immediately navigate to your 'Deleted Items' and 'Sent Items' folders and permanently delete large emails to free up quota.

Use Private Browsing or a Different Browser

Quick Tip: Sort your emails by 'Size' to quickly identify and remove the largest attachments.

Solution 2

Clear Browser Cache and Cookies

Clearing out corrupted browser data can resolve persistent QuotaExceededException login blocks.

Solution 3

Contact Your Microsoft 365 Administrator

If you are completely locked out, an administrator must intervene to adjust your quota or clear space.

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Frequently Asked Questions

What does the QuotaExceededException error mean in Outlook?

This error occurs when your Outlook mailbox has reached its maximum storage capacity. Once full, the server prevents you from receiving new emails and may block your access to the web portal entirely.

How can I check my Outlook mailbox storage limit?

If you can log in, click the Gear icon (Settings) in the top right corner of Outlook on the web, go to 'General', and then click 'Storage'. This will display a breakdown of the space you have used.

Can I delete emails if Outlook won't let me sign in?

If you are completely blocked from logging in, you cannot delete emails yourself. You will need to contact your Microsoft 365 admin to either temporarily increase your quota or use administrative tools to remove items from your mailbox.

Why does using an incognito window help with Outlook login errors?

When a mailbox is full, the browser sometimes caches the error page, trapping you in a login loop even if some space clears up. An incognito window ignores the cache and forces a fresh connection to the Outlook server.

Outlook & Email Problems