title: Are there such things as Email Hooks?
body: <p>After hearing about git commit hooks, I was thinking maybe there are such things as email hooks...</p>
  
  <p>Is it possible for me to build a program that says "hey, you just received an email, now run this ruby script"?  Something like a GMail Web Hook.  Is there anything out there like that?  I mean I could build a cron thing that checked my email all the time, but maybe there's a more formal way.</p>
  
  <p>Looking for an online email system to do this with, not say my Mac Mail.</p>