We have a MOSS 2007 production environment where we are trying to setup alerts on some lists. The problem is that the alerts are not being sent to the users. When a user sets up alerts on some site he gets the initial email saying that he has set up alerts for this site but then when changes to the site happen the user never receives any email. After some initial troubleshooting it was possible to see that the eventcache table seems to be correctly populated when new items are added or changed on the site and new records appear in this table with the eventdata not null. After the defined interval the event data will change to null so it seems that the alerts are being correctly triggered by SharePoint 2007. However no email arrives at the user.
This is very strange since the initial email is sent to the user. In the SharePoint logs no errors were detected us..Any pointer what to do next?