The following users do not have e-mail addresses specified: . Alerts have been created successfully but these users will not receive e-mail notifications until valid e-mail addresses have been provided

In SharePoint 2007 or SharePoint 2010, when a user try to subscribe to an Alert, they got the above error.

Problem:

• When you create the user in AD email address not specified
• User got added to SharePoint
• You added user’s email in AD and run the profile import
• You know see user’s email address on mysite page

But when you subscribe to Alerts/emails. You are still getting error.
Solution:

Delete the user from SharePoint and add the user again and that will fix the problem.