I learned something today that I wanted to pass along. Here at Bamboo, all day-to-day communication and collaboration occurs through SharePoint (check out my comically titled post, Who Would Have Thought that Eating your own Dog Food Could Taste so Good?), and I happened to notice a certain behavior of the out-of-the-box SharePoint Alerts feature that got me scratching my head.  What I noticed was that some of the alerts I received in Outlook contained the internal URL of our SharePoint site, while other alerts (different alert jobs, the way) used the external site URL. This behavior affects not just the hyperlinks, but the images as well. After doing some digging around (couldn’t find a relevant setting anywhere!), I began to wonder if the alert URL is based on how you’re logged in at that time of the alert’s creation.  So I logged in to one of my lists that was sending the alerts with the internal URL, deleted the Alert job, and created a new alert while logged in using the External URL.  And guess what? It worked! This also further improved the loading speed of my alerts in Outlook with the combination of adding entries into my Credential Manager.

There are two ways you can manage your alerts in SharePoint 2010:

Method 1

1. Click on your name in the top right corner of your SharePoint Site and click My Settings:
   
2. Select My Alerts from your profile page:
   
3. This page will display all alerts created for the site you’re currently in.  Select the alert(s) you want to delete and click Delete Selected Alerts. Now create a new alert (again confirm you are logged in with the external URL) clicking the option Add Alert.

Method 2

1. Open the list that has the offending alert. Click on the List tab within the List Tools grouping:
   
2. Locate the Alert Me icon and select the option Manage Alerts:
   
3. This page will display all alerts created for the site you’re currently in. Select the alert(s) you want to delete and click Delete Selected Alerts. Now create a new alert (again confirm you are logged in with the external URL) clicking the option Add Alert.

NOTE: One feature SharePoint provides is that users who have the Permission Level Manage Alerts can create alerts for you, and when such a user creates an alert, it’s based on their login URL, thus they may create alerts with an internal URL and not the external one if they are working with SharePoint within the company firewall.

As a SharePoint Administrator, another option is you can reset alert URLs for ALL users using PowerShell. This is not a recommended approach, however, as some users work with SharePoint within the firewall and others use it outside the firewall, but it is an available option.  For further details, see this post Andrew Emmanuel Toh.