I use shared web hosting for a couple of Drupal sites, using my hosting provider's MySQL database server for storage. One of the sites recently sent me a few emails that should have been written to the database, but there was no record of them.
Both yesterday and today I submitted a form on another of the sites that should have written to the database, but it didn't. There are no errors in Drupal's watchdog log though. How do I down the source of the problem?