Before any Apex callout can call an external site, that site must be registered in the Remote Site Settings page, or the callout fails. Salesforce prevents calls to unauthorised network addresses.To add a remote site setting:From Setup, enter Remote Site Settings in the Quick Find box, then select Remote Site Settings.
- Click New Remote Site.
- Enter a descriptive term for the Remote Site Name.
- Enter the URL for the remote site.
- Optionally, enter a description of the site.
- Click Save.