How to Reduce the Outlook Mailbox Size (Step by Step)

Over time, your Outlook mailbox can grow to an enormous size with incoming emails. What most people don’t realize is that an overcrowded mailbox can pose problems when you try to perform a migration of your emails to Office 365 or another cloud service provider. If you are looking for ways to reduce the outlook mailbox size, this blog has got you covered with easy to follow solutions.

Microsoft Outlook is a popular email application used by businesses across the world. Every day, hundreds of emails are received and sent out from Outlook mailboxes. With such activity, it is only a matter of time before users’ Outlook mailboxes become oversized.

Now, it is important to understand that the more a user sends and receives emails from Outlook, the larger his mailbox’s size will be. While there’s theoretically no problem with a large mailbox, it can pose problems if you plan to switch your emailing platform or service provider. Moreover, it can lead to limited performance of your mailbox software.

For example, Office 365 users get around 50GB of free storage space with their new account, but once you are about to exhaust that limit, your mailbox will start showing warnings of not being able to receive new emails. 

Thus, if your Outlook mailbox has grown extremely large in size, you should start thinking of reducing the mailbox size in order to successfully migrate to the new platform. Let’s try to see the step-by-step instructions to reduce the Outlook mailbox size.

Mailbox Cleanup

Everyone’s Outlook mailbox has at least some unwanted emails that hoard up precious space. The Mailbox Cleanup utility is aimed to get rid of such files to ultimately help reduce the mailbox size. Here are the steps to follow:

1. Open Outlook on your computer
2. Select File -> Info -> Cleanup Tools -> Mailbox Cleanup.

3. Now you’ll be prompted to initiate the scanning all your Outlook folders to determine each one’s size and find out which one is occupying a large space.
4. Click on View Mailbox Size option
5. When Outlook connects to the Exchange Server, you will see two options – Local Data and Server Data. You need to select the Local Data tab. 

Note: Any changes you make to the Local Data will also reflect in Server Data

6. Next, you need to pick Find older or larger items in the Local Data tab to select files that can be deleted directly
7. You can also use the Auto Archive option to archive older emails
8. Check the size of the Deleted Items folder and empty the folder

At this point, you should start noticing a significant decrease in your mailbox’s size already.

Save and Remove Attachments

Attachments are space-eaters and you can reduce your mailbox size to a great extent by removing unnecessary emails attachments. You don’t necessarily have to delete all attachments. You can simply save them to your local drive and remove the attachment from your mailbox. Agreed it requires you to take a few extra steps, but this can help reduce your mailbox size considerably. 

Here are the steps to follow:

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1. Open Outlook on your computer
2. Open an email that has an attachment
3. Right-click on the attachment and click on Save All Attachments. Alternatively, you can select Actions from the Message tab, and then click on Other Actions -> Save All Attachments.
4. Next, locate the folder where you want to save the attachment and click on Save
5. If you don’t need the email after saving the attachment, delete it. But if you want to retain the message after removing the attachment, right-click on the attachment and choose Remove

Archive Old Emails

There could be times when you don’t need old emails for everyday work-related tasks, but may still need to keep them safe and accessible for compliance purposes. You can archive such old emails in Outlook to not lose out on the messages but also save a good amount of your mailbox space. 

Here is how to do it:

1. In Outlook, go to File -> Info
2. Click on Tools -> Clean old items

3. You will see a pop-up box titled “Archive” on the screen
4. Select Archive this folder and all subfolders

5. Choose the folder you want to archive
6. Keep the “Do not auto archive” option unchecked. It will ensure the files you don’t want to archive are not automatically added to archive

7. Click on OK to confirm your selections

Use Stellar Migrator for Outlook

Now that you have reduced the size of your Outlook mailbox file, exporting it to another emailing platform like Outlook 365 shouldn’t be a challenge. However, if you find the above methods of reducing mailbox size cumbersome, you can skip all the hassle and use Stellar Migrator for Outlook to import your PST files to Office 365 directly. 

Stellar Migrator for Outlook is an advanced migration tool that transfers your files with complete integrity and precision. The tool can migrate PST files from multiple systems to Office 365 independent of their location and allow you to customize the migration as per your needs. Here are the steps to use Stellar Migrator for Outlook:

1. Download Stellar Migrator for Outlook from Stellar official website.
2. Install the software with default options and launch
3. Click on ‘List Profiles’ to list all the PST files configured.  Alternatively, you can select ‘Choose manually’ to browse PST location.

4. Click on Scan
5. The software will now analyze the PST file and start the scan process with progress bars.

6. After the scanning process gets completed, you need to select the mail items and folders that you want to upload to Office 365 from preview window
7. Next, click on Migrate Mailbox.
8. When prompted, enter the username and password of the licensing account to fetch the migrator software’s license.

9. Now select ‘Office 365’ and click on Next
10. Enter the Office 365 mailbox credentials and click ‘Migrate’

11. The software will now establish a secure connection with Office 365 and start migrating your PST files to Office 365.
12. Once the process completes, a message will appear to confirm the successful migration of your Outlook PST file to Office 365.

Wrapping it up

While both Outlook and Office 365 offer high performing emailing services, each one has its own set of pros and cons. Office 365 is a great productivity tool that allows users to work from anywhere and anytime as long as they have Internet connectivity. The Outlook mailbox size can be a big hindrance for users over time, pushing them to migrate their entire communications database to the new platform. Stellar Migrator for Outlook is an innovative migration tool for Outlook that can allow you to migrate your PST files to Office 365 without any hiccups.

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