How to send mails to new Drupal users after 1,7,20 days

When new users sign up on my Drupal website, I would like to send them some tips-and-tricks emails. First mail after one day, another day the next we开发者_如何学运维ek and another email after two weeks.

Is there a plugin (or a set of plugins) that can do this? I want to avoid hacking too much PHP.

thanks.

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Rules module, and its Scheduler module