The alerts / notifications in SharePoint show the links on the wrong (internal servers) URL.
The SharePoint notification function always refers to the default zone, which is set in the web application.
Need to correct the links in the zone Defaut a URL to be registered, the Internal and External DNS from a server can be resolved.
1. Navigate to System Settings> Alternate Access Mapping
2.Select the Alternate Access Mapping Collection:
3. Press the "Edit Public URLs" button:
4. Change the default URL can be resolved to a URL, the external as well as internal