I'm currently learning about the Drupal email functions, such as drupal_mail and hook_mail, and hook_mail_alter, and I have a problem before me where I'll need to be able to queue emails for delayed delivery. For example, an event signup notification that needs to wait for an hour after the event was registered by a user. And that email has user specific data, so can't be just a generic template email...

I'm using the MailQ module, mainly for it's logging capabilities, but I wonder if it (or something else) could be modified to add a configurable delay function?

Any ideas?