How to Change the Attachment Size Limit for Outlook Emails

When trying to attach a very large file to Outlook emails, you may receive a prompt that the attachment size exceeds the allowable limit. This article will teach you how to change the size limit.

If you are using an Internet email account like POP3 or IMAP, Outlook has a default attachment size limit of 20 MB. In contrast, if using an Exchange email account, the size limit is 10 MB. Thus whenever you attach files whose sizes are greater than the limit, you will definitely receive the error shown as below. You can get rid of it by changing the attachment size limit.The attachment size exceeds the allowable limit

Change the Attachment Size Limit for Outlook Emails

  1. At the very outset, you should close Outlook program and go to “Start Menu”.
  2. Then in the search field, type “regedit” and press “Enter” to access Registry Editor.Search "regedit" in Start Menu
  3. At this time, you might receive a prompt, asking if you allow this program to make changes to your computer. You can click “Yes” button.Allow This Program to Make Changes to the Computer
  4. After you entering the Registry Editor, you should find the following registry keys in sequence: “HKEY_CURRENT_USER” > “Software” > “Microsoft” > “Office” > “<version> “ > Outlook” > “Preferences”

Note: With respect to the variable “<version>”, Outlook 2007 version refers to “12.0”; 2010 version refers to “14.0”; 2013 version refers to “15.0” and 2016 version refers to “16.0”.

  1. Next right click “Preferences” key and select “New” > “DWORD Value”.Create a DWORD Value under Preferences
  2. In the right pane, you ought to rename the new generated DWORD value as “MaximumAttachmentSize”.
  3. After that, you can double click the “MaximumAttachmentSize” value to specify its value data. In the new popup dialog box, take the following steps:
  • In “Base” field, change to “Decimal”
  • Then in “Value data” field, type the size limit as per your needs. You should notice that this size is in KB. Therefore, for example, if you would like to set the maximum attachment size as 100 MB, you should enter “102400”. But if you do not hope to limit the attachment size, just input “0” in the box.Change the Attachment Size Limit
  1. Finally click “File” > “Exit” to close Registry Editor and reboot your computer. You can have a try.Attached File

Important Note: Changing the attachment size limit in Outlook does not modify the limit set by your ISP on the mail server. If their limit is set to 10MB, you will still fail when trying to send a file larger than this size. In this case, what you can do is only break down the large attachment.

Never Download Attachments from Unknown Contacts

Due to Outlook’s vulnerability, we should watch out all the potential risks, such as the viruses disguised in emails. Hence before downloading the attachments, we should make sure its security. Otherwise, the chances of Outlook corruption will be increased. In that case, you should take recourse to a specialized repair tool like DataNumen Outlook Repair, which can repair PST file without breaking a sweat.

Author Introduction:

Shirley Zhang is a data recovery expert in DataNumen, Inc., which is the world leader in data recovery technologies, including sql recovery and outlook repair software products. For more information visit

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