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The Outlook Data File Reached The Maximum Size – Rapid Solution

Published By Mohit Jha
Anuraag Singh
Approved By Anuraag Singh
Published On April 1st, 2023

The ability to work offline is very important and useful for any client if there is unreliable network connectivity. The Outlook data file reached the maximum size is a common problem due to which users can’t access the Outlook data which in turn causes a huge problem.

Outlook OST files are the most important files in the Outlook email client that help the person to work and check emails in offline storage. It’s an offline folder file of MS Outlook that allows the user to work offline and synchronize any type of changes with the Exchange server as it connects. This can be resolved by reducing the amount of data in this file storage to help the user to get access to their files easily. This could be easily performed with the help of an OST Splitter.

So in this section, we will cover all possible ways to solve the OST that has reached the maximum size Outlook 365 problem. This will help the users to work with a .ost file that is nearing its maximum size.

Table of Content

The Outlook Data File Reached The Maximum Size – Reasons Behind Error

The occurrence of such an error causes workflow hindrances. This error occurs in Outlook due to several reasons. Some reasons for this error are:

  • The OST file or ANSI-encoded PST file is getting bigger than the size limit or getting larger than the maximum 2 GB size.
  • The user’s Uni-code encoded OST file size is exceeding the size limit which is 50 GB.
  • The registry policy in place, which might have changed the limits that are there by default can cause the OST has reached the maximum size Outlook 365 error.
  • The Outlook OST files might be corrupted. The OST files might be getting affected by some malware activity causing the increase in the size of the OST file.

These are some of the most common reasons behind the Outlook data file reached the maximum size.

Also Read:- How to Automatically Forward Emails in Outlook 365? Different Ways Explained

Solutions to Handle Outlook 365 Issue Manually

The proper choice of solution for a particular problem depends on the type of scenario that is affecting the Outlook data file. Following are some of the ways that can help in finding solutions to the above-mentioned errors. Also, there is an instant solution that encompasses all the above scenarios and solves this issue.

Step 1. Determine Outlook File Data Type

  • Close all the Outlook program that is running
  • Go to Start >> Control Panel
  • Then in the Mail section, click on Data File
  • Double-click that particular Outlook data file If the “MS Exchange” window shows up, then the file is .ost
  • Now in the “Advanced” tab
  • Click at the bottom to see the message that declares “Mailbox Mode” either as Unicode or as non-Unicode
  • If the Personal Folders window comes up, then that file is a PST file
    1. If the value is “Personal-Folders-File (97-2002)”, then it is an ANSI format file
    2. If the value is “Personal-Folders-File” then it’s clearly Unicode
  • Note the type

Step 2. Locate Outlook-Data-File

The Outlook data file reached the maximum size problem can be resolved if the user can locate the problem source. In order to get the problem please ensure that there are no hidden files.

The OST files are located under this location – C:\Users\-your-username-here\AppData\Local\Microsoft\Outlook\

  • Now go to Tools in any of the Explorer windows
  • Then find Folder Options and click on View
  • Now select the radio button to Show hidden files

If MS Outlook is in use with an MS Exchange server, then there will be one or more OST files in this particular folder, else, there will be PST files.

Step 3. Convert Files to Unicode to Solve The Outlook Data File Reached The Maximum Size Issue

ANSI-Encoded PST to UNICODE Format

  • Creating a new Outlook profile to empty the PST file
  • If the version of Outlook is newer than 2003 then this new PST would be in Unicode format

Convert ANSI-Encoded OST File to Unicode Format

  • First Cached-Exchange-Mode has to be disabled
  • Rename the OST file that is in question to this name “outlook.old”
  • And now, open Outlook
  • Close Outlook now and re-enable the Cached-Exchange-Mode

MS Outlook program would rebuild the OST file in Unicode format along with data from the MS Exchange server This will solve the problem of OST having reached the maximum size Outlook 365 problem easily. 

A Professional Solution For The Outlook Data File Reached The Maximum Size Issue

This manual method is not safe to perform as deleting some important data files of Outlook can force you to reinstall the Outlook email client. This issue is sure to be resolved with the help of this expert-recommended SysTools OST Splitter Tool. This tool will help the user to split the large-sized OST files into smaller parts. You can get to see its demo model as well before finally buying the tool.

Download Now Purchase Now

Some Advanced Features of the Tool

The features provided by this software make it more advanced than any other solution present on the market. Some of these features have been listed below.

  • This tool does not require the installation of an Outlook email client to solve the Outlook data file reached the maximum size problem.
  • Different split options like Split by Date, Size, Year, Folder, Email ID, and Category provide the user with flexibility.
  • The tool can also help the user repair previously corrupted OST files before splitting them.
  • The user can add single or multiple files or even folders to the tool.
  • The user can split OST files into UNICODE PST files without any size limitations.

Steps to Solve the Outlook Data File Reached the Maximum Size Outlook 365

  1. After launching the software, add the OST file(s) using the Add File(s) or Add Folder button. Outlook data file reached the maximum size
  2. On the next screen, select the desired Split Option and Split File Size.Split ost options
  3. The Split Information screen will show the chosen settings and other details of the task. After verifying the information, click Next.Split Information
  4. The tool will start the process of splitting the OST files.Split process
  5. Once the process is completed, use the Destination Path option to access the resultant data.Destination path


The Outlook data file reached the maximum size is a problem that occurs in Outlook 2016 / 2013 / 2010 / 2007 and below versions. This problem is sure to be solved with the above-featured professional solution. The advanced features and easy-to-follow steps of the software make it the perfect utility for solving this issue. 

Frequently Asked Question

Q. Is there any way to fix the Outlook data file reached the maximum size? 

A. Yes, there are two ways to fix this issue one is the manual solution which is complicated for non-technical users, and the second is the automated way which is perfect and the easiest way to solve this problem.

Q. Does the manual solution the safe solution to fix this Outlook error?

A. If you’re in the technical field, you might use a manual solution. However, if you are not a technical user, you must opt for the automated solution.

Q. What do I do when my Outlook data file is full?

A. Follow the below steps:

  1. Click File Tabs > Click Tools > Select Mailbox Cleanup
  2. Find items older than and larger than
  3. View deleted item’s size and empty them