title: When to use various Akka Mailbox types
body: <p>I'm trying to understand when and where to use the different <a href="http://doc.akka.io/docs/akka/2.3.11/java/mailboxes.html#Builtin" rel="noreferrer">built-in Akka mailboxes</a> as well as when it is appropriate to roll your own. However, nowhere on that page does it explain what a "<strong>bounded mailbox</strong>" actually is, or how it behaves different than an <em>unbounded</em> mailbox. Also, that page categorizes mailboxes as "<em>blocking</em>" vs "<em>non-blocking</em>". And while I have a strong idea of what they mean by this (a message can be sent to a mailbox unless the mailbox is first emptied) I'm not 100% sure that I understand this. So seeing that I have no idea what the docs mean when they categorize a mailbox as bounded or blocking, it's tough for me to tell when I should be using each type.</p>
  
  <p>Also, it seems like it is the default Akka behavior to clear out an actor's mailbox if that actor is restarted. I'd like to prevent this, but not sure if the solution is to use one of these built-in mailbox types (no mention of message persistence is mentioned on this page) or to somehow use persistent actors to accomplish such lossless-ness.</p>