This document resides in a document library that is not trusted.

Issue:

User created an OOB Approval workflow to get the approval for the doc.

when user clicking on the "EDIT THIS TASK" button from outlook window the user will get the below error message on the screen

"This document resides in a document library that is not trusted.
To participate in workflows on this document, add the document library to your list of trusted sites."

Resolution:

To resolve this issue, add the domain “*.contoso.net” to the Local Intranet Zone in IE browser settings.

Weird that SharePoint Site prompt username/password to access pages:

This problem can be bypassed by modifying some settings in IE. Specifically you need to add the SPS site to the list of sites in the Local Intranet Zone as follows.

1. Open IE
2. Click on Tools -> Internet Options
3. Select Security tab
4. Select Local Intranet Zone
5. Select Sites
6. Click Advanced
7. Add the base URL for your new SPS site to the list
8. Click OK
9. Click OK again.

Once this is done you need to configure IE to automatically log in using current username and password for sites in the Intranet Zone.

This will resolve the issue and user can able to approve the workflow from outlook.