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Increase Outlook Attachment Size Limit [2024] 💥

How can I Increase the Outlook Attachment Size Limit

Picture this scenario, you've just completed an extensive report for an important client, filled with detailed analyses and high-resolution images, resulting in a file size of thirty five megabytes. With the deadline looming, you rush to your computer, compose an email in Outlook, attach the hefty report, and click "Send."

But instead of a successful transmission, you're met with the dreaded "Attachment size exceeds the allowable limit" error. This frustrating moment highlights the challenges posed by Outlook's attachment size limit, an obstacle that can disrupt even the most meticulously planned projects.


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Understanding Outlook's Attachment Size Limit

The attachment size limit in Outlook is set at 20MB per email for all versions. This means that whether you attach a single file or multiple files to an email, the total size cannot exceed the 20MB limit. If the combined size of your attachments surpasses this limit, the email will not be delivered.

Why Email Providers Limit Attachment Sizes

Email servers impose limitations on the size of attachments to ensure efficient data transmission and server performance. While Outlook sets a 20MB limit for attachments, other providers like Google and Yahoo Mail allow up to 25MB.

Attachments must be encoded into a format compatible with email infrastructure before sending. This encoding process can increase the size of an email by approximately 35%. For example, an email that is exactly 20MB could expand to around 28MB after encoding. This size limit can affect how you share files, such as sending multiple photos for a wedding to a photographer. If your attachment exceeds the allowed limit, Outlook will suggest an alternative method, such as using Microsoft's OneDrive, to send your large files.

Bypassing Outlook's Maximum Email Size Limits

Can you bypass the maximum email size limits in Outlook? The short answer is no. However, the good news is that there are workarounds available to help you send large-sized files to your recipients.

4 ways to send larger files in Microsoft Outlook

1. Compress Files to Reduce Size

One straightforward approach to bypassing Outlook's attachment size limit is to compress your files. Compressing can reduce the size of your files by approximately 20%. If you're using Windows, you can manually compress a file into a ZIP format using WinRAR. Here's how:

  1. Right-click on the file or folder you want to compress.
  2. Choose "Add to archive..." from the context menu.
  3. In the WinRAR window, select "ZIP" as the archive format.
  4. Click "OK" to create the compressed ZIP file.

Additionally, consider using tools like Weight Diet for Outlook, which automatically compresses outgoing attachments, increasing their chances of fitting within the size limit.

2. Split the File into Smaller Sizes

If compressing the file doesn't reduce its size enough to meet Outlook's attachment limit, consider splitting the file into smaller parts. For example, if you have a 24 MB file that exceeds the limit, you can use a tool like WinRAR to divide it into three 8 MB segments. You can then send each segment individually.

  1. Right-click on the large file and choose "Add to archive..." in WinRAR.
  2. In the "Split to volumes, size" field, enter the desired size for each segment (e.g., 8 MB).
  3. Click "OK" to create the split archives.

Each segment will be a separate file that you can attach and send in individual emails.

3. Modify the Registry to Increase Outlook's Attachment Size Limit

If you need to send larger attachments in Outlook and your email server supports them, you can adjust the attachment size limit by editing the Windows Registry. Follow these steps with caution, as incorrect changes to the Registry can cause system issues:

  1. Press Windows + R keys simultaneously and type "regedit" to open the Registry Editor.
  2. Navigate to the appropriate key for your version of Outlook:
    • Outlook 2007: HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\Preferences
    • Outlook 2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Preferences
    • Outlook 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Preferences
    • For later versions, replace the version number in the path accordingly (e.g., 16.0 for Outlook 2016).
  3. Find and edit the Maximum Attachment Size value, setting it to your desired limit in kilobytes (e.g., 102400 for 100MB). Set the value to 0 to remove the limit entirely.
  4. Close the Registry Editor and restart Outlook. You should now be able to send larger attachments.

Note: If the recipient's email server or your mail server does not support the size of the email you're trying to send, the email will not be delivered. For instance, if you send a 20MB email from an Outlook account to a Gmail account, the recipient will receive it, but may not be able to forward it to other addresses due to size limitations.

4. Use Cloud Storage Services for Large Files

Sending large files or numerous files is made simpler with cloud-based storage and file-sharing services. Platforms like Dropbox and OneDrive (ideal for Outlook.com users) allow you to upload files to the cloud and then share a link to the file via email. For sharing particularly large files, such as hour-long videos, there are specialized cloud video platforms that enable recipients to stream the content directly in their browser without the need for downloading.


By understanding the attachment size limits in Outlook and employing these workarounds, you can effectively manage and send large files via email. Whether it's through compressing files, splitting them into smaller parts, modifying the registry, or utilizing cloud storage services, there are multiple ways to ensure your important attachments reach their destination. For more tips on managing your Outlook inbox, including archiving old emails, check out this article.


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