Outlook - open attachments from a trustworthy source

When opening an email and there is an attachment, in my case a pdf, I get the following warning box come up. “You should only open attachments from a trustworthy source.”

open attachments from a trustworthy source

“Would you like to open the file or save it to your computer with an Open, Save or Cancel Tab to click.  The message itself is fine but the issue being faced is that to prevent this message from appearing agin, there is a box with “Always ask before opening this type of file” which I cannot unclick and is greyed out.  The below solution will allow you to clear the check box which will prevent this message “open attachments from a trustworthy source” from appearing again.


Since that option is a system wide change and not limited to the logged on user, you must perform this action with Administrator rights.If you are part of a corporate environment and the user does not have Administrator rights you will need to do so temporarily. (If you simply run the program as administrator different to the Outlook profile you will start Outlook as that administrators outlook profile.)

As Outlook runs with user-level permissions by default, even when logged on as an administrator, you must also explicitly run Outlook as an administrator to change the option.

  1. Close Outlook.
  2. Hold CTRL+SHIFT while clicking on the Outlook icon.
  3. Accepts the security prompt and/or provide administrator credentials.
  4. Open the attachment and untick the “Always ask before opening this type of file” box.
  5. Close Outlook and start it normally.

(If you have temporarily gave the user administrator rights, remember to remove once complete)

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