ified.
</p>

<p class=note>
Note: MIME headers are independent of order. Therefore, there is no problem
in representing them in a Lua table. 
</p>

<p>
The following constants can be set to control the default behavior of
the SMTP module: 
</p>

<ul>
<li> <tt>DOMAIN</tt>: domain used to greet the server;
<li> <tt>PORT</tt>: default port used for the connection;
<li> <tt>SERVER</tt>: default server used for the connection;
<li> <tt>TIMEOUT</tt>: default timeout for all I/O operations;
<li> <tt>ZONE</tt>: def