How to Increase the Outlook Attachment Size Limit

David Hughes
David Hughes
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In this guide, you’ll discover effective methods to expand the file size limit in Outlook, ensuring that you no longer face the frustrating “attachment too large” error. Additionally, we’ll explore alternative strategies for sending sizable files through Outlook and introduce how the Clean Email tool can revolutionize your email management.

Outlook File Size Limit

Outlook restricts the size of email attachments, blocking any that exceed its preset limits. To bypass this limitation, you might consider alternative file-sharing methods or adjust your system’s registry settings.

When attempting to send a file too large for Outlook’s limits, you’ll encounter this alert:

“The file you’re attaching is bigger than the server allows. Try putting the file in a shared location and sending a link instead.”

For users of Outlook 2013 and subsequent versions, the attachment size cap is set at 20 megabytes. Exceed this, and your email won’t send. Those with a Microsoft Exchange Server Account face even stricter constraints, with a maximum of 10MB per attachment. You can check and adjust these limits in your Transport Settings Properties if you have access to an Exchange Mailbox.

Before modifying your Registry Editor to increase attachment size limits, always back up your registry to safeguard your data against potential errors.

Feeling overwhelmed by Outlook? Don’t worry—check out our comprehensive guide on mastering Outlook for smoother, more effective email management.

How to Increase Outlook Attachment Size Limit

The default attachment size limit in Outlook is 20MB, which can be restrictive when trying to send larger files. While it’s generally advised not to alter this limit on your own, there are ways to increase it by modifying your system’s registry settings.

Here’s how you can either adjust the size limit permanently or explore alternatives for sending larger files without modifying the registry.

Adjusting the Maximum Attachment Size in Windows

To change the limit within Windows, follow these steps carefully:

  • Open the Registry Editor:
    • Press Windows + R to open the Run dialog.
    • Type regedit and click OK to launch the Registry Editor.
  • Navigate to Your Outlook Version’s Entry:
    • For Outlook 2019 and 2016, go to: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences
    • For Outlook 2013, visit: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Preferences
    • For Outlook 2010, access: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Preferences
  • Modify the Maximum Attachment Size:
    • Double-click on MaximumAttachmentSize. If it doesn’t exist, create it by right-clicking, selecting Edit → New → DWORD Value, and naming it MaximumAttachmentSize.
    • Enter your desired limit in the Value Data box and click OK.
  • Restart Outlook: Close the Registry Editor and reopen Outlook to apply the changes.

Modifying Attachment Size on Mobile Devices

Currently, it is not possible to change the attachment size limit on mobile versions of Outlook. You’ll need to make adjustments through the web or desktop versions of the Outlook application.

How to Send Large Files Through Outlook

If adjusting the Registry Editor seems daunting or isn’t feasible, here are straightforward strategies to send larger files without changing system settings.

1. Compress Your Files

  • Simple Compression: Right-click on the file you wish to send and select ‘compress’. You’ll have a few options to choose from, making it easier to fit within Outlook’s size limits.
  • Use an Add-in: Consider installing an add-in like Weight Diet for Outlook, which automatically compresses files as attachments. This ensures they are more likely to fit within the permissible email size.

2. Split the File

  • Use a Compression Tool: Tools like 7-Zip can split a large file into manageable pieces, typically around 7MB each. This method is effective for bypassing file size limits.
  • Caveats to Consider: While splitting files can be a practical solution, be cautious as it may alter the files slightly. It’s best used when file integrity is not compromised by segmentation.

3. Send Files via Cloud Storage

Utilizing cloud storage services such as Dropbox, OneDrive, iCloud, or Google Drive is often the most efficient way to send large files without modifying file sizes or registry settings. This method preserves the original file’s integrity and simplifies the sending process.

How to Use Cloud Services with Outlook:

  • Choose a Cloud Service:
    • Popular options include OneDrive, Dropbox, iCloud, and Google Drive.
  • Upload the File:
    • Navigate to your chosen service and upload the file. For instance, if you’re using Dropbox, drag your file into the Dropbox folder or use the web interface.
  • Share the File:
    • Once the file is uploaded, copy the link provided by the cloud service.
    • Paste this link into your Outlook email as you would with any text.
  • Recipient Access:
    • The recipient can simply click the link to download the file directly to their computer.

Integrating SharePoint:

  • If SharePoint is part of your workplace ecosystem, the process is similar: upload the file to SharePoint and share the link via email.

Additional Tip for Large Images:

  • To send large images without using cloud services, you can reduce their size directly in Outlook:
    • Attach the image to your email.
    • Go to File → Info.
    • Under Image Attachments, select ‘Resize large images when I send this message.’
    • Proceed to send your email normally.

Choosing Between Outlook and Gmail?

  • If you’re deciding between using Outlook or Gmail, consider checking our detailed comparison to see which service better suits your needs.


Managing and sending large files via Outlook doesn’t have to be a struggle. By exploring the methods outlined in this guide—from modifying registry settings to utilizing cloud services—you can effectively bypass Outlook’s default size limitations. Whether you choose to compress and split files, adjust settings directly in the Windows Registry, or leverage the power of cloud storage solutions like OneDrive or Dropbox, each approach offers its own advantages.

Remember, the key is to choose the method that best aligns with your technical comfort level and the integrity requirements of your files. For those who frequently share large files, integrating cloud services into your daily workflow can simplify the process significantly. As always, consider the security implications of your chosen method, especially when dealing with sensitive or proprietary information.

By adapting these strategies, you can ensure that your communications remain efficient and uninterrupted, regardless of the file sizes you need to send.


What is the default file size limit for attachments in Outlook?

The default size limit for email attachments in Outlook is 20MB for newer versions (Outlook 2013 and later). For users with a Microsoft Exchange Server Account, the limit is typically 10MB per attachment.

How can I increase the attachment size limit in Outlook?

You can increase the attachment size limit by modifying the registry settings on your Windows computer. Navigate to the Registry Editor and adjust the MaximumAttachmentSize value for your specific Outlook version. Always back up the registry before making changes.

Are there any risks associated with modifying the registry to increase the attachment size?

Yes, modifying the registry carries risks such as potential data loss or system instability if not done correctly. It’s important to back up your registry before making any changes and follow detailed instructions carefully.

What are some alternative methods for sending large files via Outlook if I don’t want to edit the registry?

Alternative methods include compressing files, splitting large files into smaller segments, or using cloud storage services like Dropbox, OneDrive, or Google Drive to share a link to the file instead of attaching it directly to the email.

How can I send large files through Outlook using cloud storage?

Upload the file to a cloud storage service, obtain a shareable link, and then insert this link into your Outlook email. The recipient can download the file directly from the cloud service. This method avoids the need to alter file sizes or Outlook’s configuration.

Is there a way to send large image files through Outlook without using third-party services?

Yes, you can reduce the size of image attachments directly in Outlook. Attach the image, go to File → Info, and select ‘Resize large images when I send this message.’ This will automatically reduce the size of the images to fit within Outlook’s sending limits.

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