Migration, as in you moved your production site from Server A to Server B.
Simply moving the site from one server to another does not mean that things outside the site move with it.
Most people have a scheduler running cron.php for email collection (the alternative is piping). Did you setup a scheduler to run cron.php on the new server?
Or do you mean upgrade? As in going from version X to version Y.
If you did that then did you change your scheduled task to run and point to the new location if you changed the folder name?
