Outlook 2013 file attachment error when file size exceeds limit

The file you’re attaching is bigger than the server allows.” error message will be shown when a user tries to attach a file which is over 20 MB. As suggested in the message the best solution is to copy the file to a shared location and send the link to the recipients. Another alternative is to archive the file and see if it can be reduced below 20 MB (20 MB is default attachment size limit.)

attachment limit error in Outlook 2013

But if you still want go ahead and still attach the file then you can try out the below registry hack. Please note that this hack only for the client side and all mail servers would still have rules to check file size limit.

Launch Registry on Windows 8

For this demo, the registry changes are done on Windows 8 system. Right click on Start button, select Run from the menu.


In Run window type Registry and click OK button to open Registry.

Open Windows Registry on Windows 8

Windows Registry changes needs to be done with caution. Do it at your own risk.

Registry changes on Windows 8 for Outlook 2013 attachment limit

In the Registry application, navigate to COMPUTER –> HKEY_CURRENT_USER –> Software –> Microsoft –> Office –> 15.0 –> Outlook –> Preferences. (HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Preferences).

Registry hack on Windows 8 to increase attachment limit in Outlook 2013

Right click on Preferences and select New then DWORD (32-bit and 64-bit based on your operating system installation).


Enter the name of the key as MaximumAttachmentSize. Then double click the newly added key and add Decimal Value as 25600 (if you want to increase the limit to 25 MB (25 * 1024)).

Maximum Attachment Size in Outlook 2013


Click OK button to confirm and apply the changes. This registry hack should allow you to insert attachment file size up to 25 MB in Outlook 2013.

Also see: How to insert attachment with email message in Outlook 2013

In Category: MS Office, Office 2013, Outlook 2013

Ravi Shankar

A Software developer and blogger who is always looking to provide technical help to the wider community.

Show 3 Comments
  • Catalin November 27, 2014, 5:59 pm

    Could you please let me know how to do this in Win 7 ? I don’t find the MaximumAttachmentSize listed there… Thank you

  • Ravi Shankar November 28, 2014, 8:00 am

    Could you please launch registry editor on windows 7 and add the registry key.

  • Andrew July 27, 2016, 8:33 pm

    what is the value for more than 35mbs? 102400?

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