Now I will talk about alerts, this happened in a farm of our customers, and it’s very easy to apply, but for us was very difficult to realize what was going on.
Ok, first imagine you have a Web Application (http://example) and then by your customer requirements it is necessary to extend the web application to http://thisisanexample, in our case we needed to extend the application to other that uses ADFS, so all the users will access trough ADFS, but the url for the alerts will point to the NTLM zone.
Easy isn’t it? Ok… but imagine that one user (or several) had configured alerts for a document library, so what will be happen?
The sharepoint alerts will be pointed to http://example but your requirement is that all users access by the url http://thisisanexample and all urlalerts point to http://thisisanexample.
So, what we can do? Delete all the existing alerts and create a new ones in the new url? Nope! Use Powershell!! yeeeep!
In this case we will point all the url alerts to http://thisisanexample, so let’s go!
$web = get-spwebapplication = "http://thisisanexample"
$web.externalurlzoneforalerts=$true
$web.externalurlZone = "Intranet"
The last piece of code can be changed depending of your needs (Internet, Custom, Default…)
Hope it helps!
Albandrod's Memory 