Problem:
The alerts / notifications in SharePoint show the links on the wrong (internal servers) URL.
Solution:
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
