Outlook Mailbox Size Limit Exceeded Error: Causes and Solutions

“Outlook mailbox size limit exceeded” error indicates your mailbox has reached its maximum storage size and crossed allowed quota limit. Once the mailbox exceeds the allocated limit, you may not be able to send and receive emails, synchronize folders, and your Outlook becomes slow and faces multiple errors.

The solution depends on the root cause of storage issue, which means sometimes mailbox hosted on mail server is full, while in other cases the local Outlook PST file grows with data. However, archiving old emails, deleting unwanted items, emptying trash or spam folders, removing and saving large attachments separately, and compacting Outlook data files can resolve this issue.

This guide explains why it happens, how it affects Outlook, and the most effective ways to fix “Outlook mailbox size limit exceeded” without risking data loss.

Understanding of Outlook Data Files

MS Outlook stores data in two different formats which depend on the account type:

• PST (Personal Storage Table): When Outlook connects with POP accounts, it stores data and archived mailboxes in PST file.
• OST (Offline Storage Table): It’s an offline copy of mailbox data that is stored on mail server. Outlook creates it when it connects with Microsoft 365, Exchange, and IMAP accounts

These files are used to store Outlook profile data, and both continue growing as mailbox data increases. And data file size depends on the Outlook version such as:

Registry settings can increase these limits, but Microsoft doesn’t support it, because it makes your file extremely large difficult to manage and can permanently damage files.

How to Fix Outlook Mailbox Size Limit Exceeded Issue?

We have used 9 different techniques to resolve mailbox issue. First, you can start from simple techniques such as deleting data, removing them from Spam and Trash folders, saving attachments separately and deleting duplicate emails to smart ways to archive old emails, and compact PST files. If nothing works, then you can divide your files for easy to organize and manage your mailbox.

# 1: Delete Unnecessary Emails

This is the simplest technique to reduce Outlook mailbox size by deleting unwanted emails. We received 1000s of emails on daily basis, which plays an important role in large mailbox size. So, we can remove unnecessary emails by following mentioned steps:

1. Open your Outlook.
2. Open any folder that contains unwanted emails.
3. Sort them by date and size.
4. Select them and use “Delete” button.

Tip: Try to remove emails with large attachments first to fix the “Outlook mailbox size limit exceeded” issue.

# 2: Empty Deleted and Spam Folder

Deleting emails and items doesn’t reduce PST file size immediately. Because Outlook moves deleted items into Deleted folder for next 30 days. On the other hand, promotional emails directly land in the Spam folder.

You can empty both folders to delete data permanently and free up storage space.

# 3: Remove and Save Attachments Locally

Large attachments are the main cause of “you have exceeded the size limit on your mailbox Outlook” issue. Find emails that contain large attachments, save them locally and remove them from mailbox by following steps:

1. Open email containing attachment.
2. Right-click on attachment and choose “Save As”.
3. Save it to any destination.
4. Again, right-click on “Attachment” and choose “Remove Attachment”.
5. Save the email.

# 4: Fix Outlook Mailbox Size Limit Exceeded by Archiving Old Emails

If you rarely access older emails, then archiving them is a more effective way than deleting them. Archiving means keeping your emails separately in a PST file which reduce the mailbox size.

1. Select the “File” from “Info”.
2. Choose “Tools” >> “Clean Up Old” Items.
3. Select the folder that you want to archive.

   

4. Select a date range for emails older than.
5. Choose any location to save the archive file.
6. Hit the “OK” button.

You can enable AutoArchive to organize your mailbox for future to fix Outlook mailbox size limit exceeded:

1. Head to the “Options” from “File” tab.
2. Open the “Advanced” tab.
3. Choose “AutoArchive Settings” from “AutoArchive”.
4. Enable “Run AutoArchive every” and select the desired interval.
5. Now configure the archive settings and save the changes.

# 5: By Splitting Large Files

Archive emails option could be a better choice for smaller data, because archived PST can itself become very large over time. So splitting is the best way to handle large data files into smaller parts. But manually it is not possible, so you can use SysTools PST Splitter Tool.

This software can divide large files into smaller parts by size, date, year, folder, category, email ID, sender and subject. It doesn’t delete any data and doesn’t affect original elements and hierarchy. It supports all file sizes from 1 MB to 1 TB without crashing. This is the best way to resolve “Outlook mailbox size limit exceeded” issue easily.

These are the steps to resolve Outlook storage space issue:

1. Download the software on the machine.
2. Upload your large data files.
3. Select the location to save output.
4. Choose any “Split Option”.
5. Select “Start” button to start process.

# 6: Outlook Mailbox Size Limit Exceeded Fixed by Compacting Large PST

The compact now option helps to reduce available white space in the data file. Follow given steps:

1. Navigate to “File” > “Account Settings” > “Account Settings” in Outlook.
2. Choose “Date File” tab.
3. Select your PST file.
4. Hit on the “Settings” >> “Compact Now” option.

# 7: Delete Duplicate Emails

Duplicate emails in Outlook mailbox are another reason for the ” Outlook mailbox size limit exceeded issue. But finding and removing them manually is a tedious task. In such case, you can use the SysTools Outlook duplicate remover tool. It helps to find and remove all duplicate emails from the file without harming original file. Not only emails, but it can scan complete mailbox including contacts, calendars, notes, and journals.

# 8: Using Mailbox Cleanup Tool

Mailbox Cleanup is a built-in feature of Outlook that helps to analyze the mailbox storage such as locating large emails, older messages, and displaying folder sizes.

1. Choose “File” tab in Outlook.
2. And then, select the “Tools” >> “Mailbox Cleanup” option.
3. Select “View Mailbox Size” for checking folder sizes.
4. Find large emails then a specific size.
5. Now, search for older emails.
6. Next, empty deleted items folder.

# 9: Fix Outlook Mailbox Size Limit Exceeded using Registry Editor

Outlook allows increasing the maximum PST file size by modifying Windows Registry. This method doesn’t work with Microsoft 365 or Exchange mailboxes.

Important Note: Incorrect registry changes can cause system issues. Also, extreme large size can damage your file. Having a backup is mandatory before making any changes.

1. Open regedit.
2. Navigate the Outlook version key.
3. Create or modify the following DWORD values:
   • MaxLargeFileSize
   • WarnLargeFileSize
4. Put the desired values (in MB).
5. Close “Registry Editor” and restart your Outlook.

For complete steps with all details, you can check this blog to increase PST file size.

What If Data Files Become Corrupt Due to Crossed Size Limit?

Outlook mailbox size limit exceeded issue can directly affect your data files and make it damaged, which is normal. Microsoft Outlook provides a tool to repair damaged files called ScanPST.exe. It can fix minorly corrupt data files by scanning them.

But there is no possible way to fix severely damaged files. In such cases, you can take help of professional solutions. SysTools PST Recovery Tool helps to fix and recover data from corrupt data file into healthy format.

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To repair Outlook OST file, use SysTools OST Recovery Tool. This software helps to fix corruption and supports inaccessible and orphaned files. It helps to restore data from damage file into healthy PST, PDF, HTML, EML, and MSG formats.

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Conclusion

The Outlook mailbox size limit exceeded error is a warning message that your Outlook data file has reached the maximum size. In this blog, we have discussed resolving it by deleting unwanted data, archiving older emails, compacting data files, and splitting large PST files.

Manual methods are simple tricks to reduce size for short time. For permanent solution, you can use smart tool to divide your file into manageable parts. We have covered all information with safe and secure techniques.