The “Message Store Has Reached Its Maximum Size” error on Microsoft Outlook can lead to users not being able to receive incoming mails or send outgoing mails when using Outlook.


The issue is usually caused by the PST file exceeding the specified storage limit. However, there are also other possible causes of this problem. Read on to find out the various causes and learn six solutions to help you resolve this error.  

Causes of “Message Store Has Reached Its Maximum Size” Error 

Causes of Message Store Has Reached Its Maximum Size Error

The causes of this error may be due to several factors such as:

  • Outlook reaches its defined storage space limit.
  • A corrupted OST or PST file.
  • Malware or viruses.

 The most common cause of this issue is a large OST or PST file. These large files lead to Outlook reaching its maximum defined storage capacity quickly. Now that you know the possible causes, let’s look at six solutions to this issue.

Method 1: Archive Data

This method involves altering settings in Outlook to decrease the storage by archiving data. First, let’s go over the steps.
Step 1: Launch Microsoft Outlook. Then, select the “File” option.
Step 2: In the top left corner, you’ll see the “Info” option. The “Tools” option can be found in the “Info” section.
Step 3: When you click on “Info,” select “Clean Up Old Items” will appear. 

Causes of Message Store Has Reached Its Maximum Size Error - Archive Data

Step 4: Check the “Archive this folder and all subfolders” box that pops up. Then, check the box “Do not AutoArchive“‘ at the bottom of the Archive box. Choose a date and select “OK” to see if the problem has been resolved.

Method 2: Export or Import Oversized PST File

 Another viable option for resolving the problem is exporting or importing oversized PST files. 

Step 1: Select “Data Files” to import or export the large PST file. When the “Data Files” section appears, select the “Add” tab.

Step 2: For the PST file, input a name that ends in “.pst” and select “OK.” A new PST file will become visible in the “‘Data Files” box.

Step 3: Afterward, go to the “File” menu and select “Open & Export.” The “Import/Export” option will appear.

Causes of Message Store Has Reached Its Maximum Size Error - Export or Import Oversized PST File

Step 4: When you select the option, the “Import and Export Wizard” will appear. Choose “Export to a file” from this menu and click “Next.”

Step 5: See the latest created “.pst” file here. Click on it and then select “Next.”

Step 6: In the “Export Outlook Data File” box, select “Include subfolders” and click “Next.”

Step 7: The “Browse” section will now become visible. Browse through and select “Do not export duplicate items.” Lastly, click the “Finish” button.

Method 3: Modify Registry Editor 

 Exit Outlook and modify the Registry Editor. Here are the steps involved:

Step 1: To begin, click on the Windows key and R simultaneously. Afterward, “Run” will pop up. Then, in the “Open” box, input “regedit” and press the “OK” button.

Causes of Message Store Has Reached Its Maximum Size Error - regedit

Step 2: Copy and paste the following path into the Registry Editor:


If “PST” does not appear, right-click the Outlook key. Then, expand “‘New.” The “Key” option should now appear. Ensure you select the option. Afterward, a new key will appear. Rename this new key to “PST.”

Step 3: On the right-hand side of the display, you’ll see the “MaxLargerFileSize” and “WarnLargerFileSize” options. 

Causes of Message Store Has Reached Its Maximum Size Error - MaxLargerFileSize

Step 4: Now, double-click the “MaxLargerFileSize” option. An “Edit DWORD (32- bit) value” window will pop up. Edit the value data and choose “Decimal.” Outlook features a 50GB storage limit, so enter 51,200 into the Value data space.

Step 5: Next, double-click the “WarnLargeFileSize” button. The “Edit DWORD (32-bit) value” tab will appear again. Edit the figure in the value data and choose “‘Decimal.” Then, enter 48640 as the value data for this parameter.

Method 4: Compact the PST/OST File

 Here we’ll show you a quick method for reducing storage data. First, let’s outline the steps below: 

Step 1: Relaunch Outlook. Go to “File” and then “Info.” A new section called “Account Settings” will pop up. Browse through, and you’ll find another option called “Account Settings.

Step 2: When you select “Account Settings,” a new tab will appear. Then, select “Data Files.”

Step 3: Next, select “Settings,” located in the “Data Files” folder.

Step 4: Afterward, an “Outlook Data File” interface will be visible. The “Compact Now” button will be located here. Lastly, press the “OK” button.

Causes of Message Store Has Reached Its Maximum Size Error - Outlook Data File

Method 5: Use Online Mode

 You can also change the connection mode from Cached to Online to resolve this error. Here’s how.

Step 1: Launch Outlook and go to the “File” menu. Afterward, go to “Account Settings” and locate “Account Settings.”

Step 2: Choose your account in the Email tab, then select “Change.”

Step 3: Select “More Settings” from the “Exchange Account Settings” window.

Causes of Message Store Has Reached Its Maximum Size Error - Use Online Mode

Step 4: Go to the “Advanced” section and uncheck the “Use Cached Exchange Mode” checkbox.

Method 6: Update Outlook

Step 1: Launch Outlook and go to the “File” menu.

Step 2: Select “Office Account” and click “Update Options.”

Step 3:  Select “Update Now” from the drop-down menu to update Outlook.