What tools are available to develop an "inmail" solution?
<p>I want to build an application that offers an "inmail" like feature that is available in financial and other applications. </p>

<p>Is there a toolset these are all based to use? Or is this all customized?</p>

<p>I reviewed a bit of XMPP, but that deals with Chat it seems, and not email.</p>

<p>I wanted to be able to send emails as well, but mostly the inmail would be used from user to user within the application domain.</p>
