• Outlook gives an error pop-up about the attachment 
  • Attachments do not get uploaded 


  • A single attachment is added exceeding the limit of 20 MB
  • Multiple attachments are uploaded and the total exceeds 20 MB


  1. Exit Outlook.
  2. Start Registry Editor.
  3. Locate and then select one of the following registry subkeys:


    HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\ x.0 \Outlook\Preferences

    Note: The <x.0> placeholder represents your version of Office (16.0 = Office 2016, Office 2019, Office LTSC 2021, or Office 365, 15.0 = Office 2013). Manually create the path in the registry if it does not currently exist.

  4. Add the following registry data under this subkey:

    Value type: DWORD
    Value name: MaximumAttachmentSize
    Value data: An integer that specifies the total maximum allowable attachment size. For example, specify 30720 (Decimal) to configure a 30-MB limit.

    Note: Specify a value of zero (0) if you want to configure no limit for attachments.

  5. Exit Registry Editor

  6. Start Outlook.