How to increase Attachment Size Limit in Outlook – Explained

While Outlook users have a 20MB cap on the file size of their attachments, they can only mail file(s) as big as 20MB in one email. Even with the latest Outlook versions, this size limit still exists.

The attachment size exceeds the allowable limit

Every time you try and attach a file that exceeds the file size limit in Outlook, you will get an error message. However, there is a way to get around this. With a little bit of creativity, you can manage to attach files that are larger than the maximum file size limit in Outlook.

Related Post: How to fix Error Code 0x80190194

Sometimes when you’re trying to upload a file bigger than the maximum limit on Outlook, a dialog box pops up advising you to upload the file in a shared location and share its link, like Google Drive. Sharing the file in a shared location and sharing the link may be a feasible solution, but it isn’t the quickest one and can be interrupted.

How to increase the attachment size limit in Outlook?

The process is very simple and should take just a couple of minutes. We will be making the change using the Windows Registry Editor. Please back up your Registry configurations before making any changes. Let us begin:

  • Open the Run dialog box and in the blank space type ‘Regedit.exe’
  • Then, depending on the version of Outlook you have running on your PC, navigate to the relevant key. For Outlook 2019 and Office 365, the key is:


Original Once you’re there, right-click in the blank area and create a new key (32-bit DWORD Value) by the name of Maximum Attachment Size.

  • It’s possible that a key with the same name already exists on this page. In that case, you can move on to the next step.
  • Now, right-click on this key and select Modify

To change the maximum attachment size in Outlook, go to the File tab and then click Options. In the Advanced settings section, under Attachments, click the Valley button. Enter the desired attachment size in Kilobytes. 1MB=1024KB, so make the calculations accordingly.

I’ve changed the maximum file size to 30MB. If you want to completely disable the limit, simply keep the value data equal to 0.

You can also make the desired changes to your Registry without using the Registry Editor by running the script below using the Command Prompt.

The following command line will allow you to change the maximum file size in Outlook to 40MB.

reg add HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences\ /v “Maximum Attachment Size” /t REG_DWORD /d 40960 /f

reg add HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Profiles\Outlook\Preferences\ /v “Maximum Attachment Size” /t REG_DWORD /d 40960 /f

As mentioned before, creating the desirable registry key and setting the bit value is the key to success. After you have completed these steps, restart your PC and Outlook should now be able to upload files that are smaller in size. This can only work if the recipient’s email provider also allows attachments of these sizes; otherwise, while the email might leave you, the recipient’s email provider may reject it and the email will bounce back.

How do I compress a file to email it?

The problem with files being too big for mail can be solved by being able to compress them. This is quite an elementary thing to do. As long as the receiver of the file has a tool to decompress your file, the purpose is pretty much resolved.

  • Open File Explorer and select the file or files you want to compress
  • Once selected, right-click on them, and from the list of options, hover your mouse over ‘Send to’
  • From the resultant drop-down, select Compressed (Zipped) Folder

Hope this article was of help to you!

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