How to Increase Mailbox Size in Microsoft Outlook & Outlook.com

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A step-by-step guide to expanding your Outlook mailbox’s capacity
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When using the Outlook desktop app, your mailbox size (PST & OST files) is limited to 50 GB. If needed, you can increase the mailbox size by editing the Windows registry—however, this is only possible in Outlook 2016 or earlier, and you can't do it on a Mac. If your Outlook.com email is full, you can free up space, or increase your storage to 100 GB with Microsoft 365. Read on to learn how to increase the size of your Outlook mailbox, plus how to increase your Outlook.com inbox size.

Increasing Mailbox Size in Outlook

If your mailbox file hits the 50 GB limit, you can increase the size by editing the MaxLargeFileSize and WarnLargeFileSize entries in the registry. In Outlook 2016, create these DWORDs in HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST and specify a size in MB (e.g., 75000 for 75GB).

Section 1 of 2:

Increasing Mailbox Size in Outlook 2016 & Earlier

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  1. If you're using the desktop version of Microsoft Outlook for Windows and have Office 2016 or earlier, you can increase your mailbox size for PST and OST data files beyond the 50 GB limit by editing the registry. To open the registry editor, press the Windows key, type regedit , press Enter , and click Yes to confirm.
    • It is not possible to increase the mailbox size in Outlook 2019, Outlook 365, or any version of Outlook for Mac.
    • We don't recommend increasing the size much higher than 50 GB, as too large of a file puts you at risk of corrupting the entire mailbox.
    • Before you edit the registry , we recommend making a backup so you can undo your changes if needed. To make a backup, go to File > Export , choose a location, name the backup, and click Save . [1]
  2. It’s in the left column. Several options will expand below.
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  3. You may have to scroll down a little to see it. A list of software manufacturers will appear.
  4. More folders will appear.
  5. A list of Microsoft products will appear in the right column.
  6. The expanded folders will now show a few different version numbers.
  7. Each version number corresponds to a release: [2]
    • 11.0 for Outlook 2003
    • 12.0 for Outlook 2007
    • 14.0 for Outlook 2010
    • 15.0 for Outlook 2013
    • 16.0 for Outlook 2016
  8. You may or may not see this under the version number. If you don't see an Outlook folder under your version, you will need to create it. To do so:
    • Click the version number once in the left panel.
    • In the right-panel, right-click a blank area and select New > Key .
    • Type Outlook and press Enter .
  9. Again, this folder may not appear for everyone. If it doesn't, you will have to create a new key:
    • Click Outlook once in the left panel.
    • In the right-panel, right-click a blank area and select New > Key .
    • Type PST and press Enter .
  10. Here's how:
    • Select PST in the left panel.
    • Right-click a blank area in the right panel and go to New > DWORD 64-bit Value (or the 32-bit option, depending on your version of Windows ).
    • Type MaxLargeFileSize and press Enter .
  11. The process is the same as MaxLargeFileSize, just a different name:
    • Select PST in the left panel.
    • Right-click a blank area in the right panel and go to New > DWORD 64-bit Value (or the 32-bit option, depending on your version of Windows ).
    • Type WarnLargeFileSize and press Enter .
  12. A dialog will appear.
  14. For example, to increase the mailbox size to 75GB, type 75000 into the “Value data” field.
    • The default mailbox size for Outlook 2013 or 2016 is 50 GB. The default for Outlook 2003, 2007, and 2010 is 20 GB.
  15. Now you'll do something similar for this other DWORD.
  16. Despite its name, setting a maximum amount here will not warn you when you get close to your limit. Instead, Outlook will attempt to make the file more compact by prompting you to delete or archive messages. You will not be able to copy or move messages within the file until you can reduce the file size. [3]
    • For example, you may want Outlook to prompt you to delete some messages when you're nearing 72000 MB.
    • Select decimal if not selected by default.
    • Once you're finished, restart your computer to ensure the changes take effect.
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Section 2 of 2:

Increasing Outlook.com Inbox Size

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  1. If you're getting an error like "Quota Exceeded" or "Mailbox Full" when you're using your Outlook.com, Live.com, Hotmail.com, or other Microsoft email address, you're running into your account's storage limit. Free Outlook accounts get 15 GB of storage, which is totally separate from your OneDrive files . [4] You can clean up your mailbox by deleting emails you don't need to reclaim some of that space. Here's how:
    • Log in to Outlook.com and click the gear icon at the top-right.
    • Click the Account tab.
    • Click Storage .
    • Expand the Email storage section if not expanded. You'll see a list of email folders and the space their messages take up.
    • Click Empty next to a folder, such as "Deleted" or "Junk Email," and select a timeframe. For example, to delete all messages in the trash that have been there for 3 months or longer, select 3 months and older . Or, you can click All to delete all messages in a selected folder.
    • Click OK to confirm. Once the messages are removed, the space they were taking up will be available again in your inbox.
  2. If you have a lot of email attachments , you can instantly reclaim space by moving them to OneDrive. Here's how:
    • Click Inbox , or select a different mailbox.
    • Click the Sort menu (the two arrows) above the message list and select Size . This displays the messages in the selected folder in size order, with the largest messages at the top.
    • Select a message with an attachment.
    • Hover your cursor over the attachment, then click the down arrow that appears.
    • Select Save to OneDrive .
    • Delete the original email and attachment, then clear your Deleted Items folder by clicking the three dots next to "Deleted Items" and selecting Empty .
    • Repeat for other large attachments.
  3. Another way to get more space in your inbox is to delete incoming messages from particular senders automatically. Just select an email in your inbox from a sender you don't want to receive messages from, click Sweep on the menu bar, and you can choose to move all messages from that sender to the "Deleted items" folder. Then, clear your deleted items by clicking Deleted Items in the left panel, clicking the three dots next to its name, and selecting Empty . [5]
    • This will also delete any messages in the current folder from the selected sender.
  4. If you don't want to delete any emails, your other option is to increase your storage limit by upgrading to Microsoft 365. You can get Microsoft 365 for $69.99/yr (or $6.99/month) for one person, or opt for a family subscription (up to 6 users) for $99.99/yr (or $9.99/month). To upgrade, go to https://www.microsoft.com/en-us/microsoft-365/buy/compare-all-microsoft-365-products?ocid=cmmngsvfl1e&rtc=1
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      References

      1. ↑ https://support.microsoft.com/en-us/topic/how-to-back-up-and-restore-the-registry-in-windows-855140ad-e318-2a13-2829-d428a2ab0692
      2. ↑ https://support.microsoft.com/en-us/topic/how-to-configure-the-size-limit-for-both-pst-and-ost-files-in-outlook-2f13f558-d40e-9c2a-e3b6-02806fa535f4
      3. ↑ https://support.microsoft.com/en-us/topic/how-to-configure-the-size-limit-for-both-pst-and-ost-files-in-outlook-2f13f558-d40e-9c2a-e3b6-02806fa535f4
      4. ↑ https://support.microsoft.com/en-us/office/storage-limits-in-outlook-com-7ac99134-69e5-4619-ac0b-2d313bba5e9e
      5. ↑ https://support.microsoft.com/en-us/office/organize-your-inbox-with-archive-sweep-and-other-tools-in-outlook-on-the-web-49b26f63-6399-4b4a-a580-14b9b1efe96d

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