Outlook Error Codes

How to Fix Outlook Message Store Maximum Size Error

Camila Milosovich Oct 1, 2026 869 views

Question details

The user is unable to manage, delete, or move emails because Outlook displays a message store maximum size error.

How to Fix Outlook Message Store Maximum Size Error

Product: Microsoft Outlook
Device & OS: not provided
Scenario: Attempting to organize emails, receive new messages, or delete old threads when the mailbox data file has reached its maximum storage threshold.
Observed behavior: Outlook freezes and prevents any messages from being deleted or moved, indicating the message store, PST file, or mailbox has reached its size limit.

Before you start

Verify your email account type (Exchange, IMAP, or POP) and locate your current PST or OST file path before attempting to compact or repair the data.

Solution 1Recommended

Clean Up Mailbox and Compact PST Data File

Use this method to permanently remove large files and compress the data file to immediately free up space.

When your mailbox is entirely full, standard deletion moves items to the Deleted Items folder, which still consumes space. You must use hard deletion and then compact the file to shrink its physical size on your disk.

Permanently Delete Unnecessary Emails

Select the emails with large attachments you no longer need. Hold down the 'Shift' key while pressing 'Delete' on your keyboard to permanently remove them and bypass the Deleted Items folder.

Empty Deleted Items

Right-click the 'Deleted Items' folder in your Outlook sidebar and select 'Empty Folder' to clear any lingering files.

Compact the Data File

Navigate to File > Account Settings > Account Settings. Go to the 'Data Files' tab, select your PST file, click 'Settings', and then click 'Compact Now'.

Clean Up Mailbox and Compact PST Data File

Compaction Time: Compacting a large PST file may take several minutes. Do not close Outlook until the process is fully complete.

Solution 2

Repair Corrupted Outlook Data Files via ScanPST

If compacting fails or Outlook continues to freeze, repairing the PST file can resolve structural errors causing the size limit issue.

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Frequently Asked Questions

Why can't I delete emails when my Outlook mailbox is full?

When a mailbox or PST file reaches its strict maximum size limit, Outlook lacks the temporary storage required to process the move command to the Deleted Items folder. You must use 'Shift + Delete' to permanently remove items without moving them to the trash first.

What is the maximum size limit for an Outlook PST file?

By default, Outlook 2010 and newer versions have a PST and OST file size limit of 50 GB. However, mail servers or local IT administrators can impose lower restrictions via Group Policy or Exchange server settings.

Does the 'Compact Now' feature delete my saved emails?

No, the 'Compact Now' function only reclaims empty space left behind after you have deleted emails or removed large attachments. It shrinks the physical size of the data file without removing your active messages.

Microsoft Office Error Codes