Many SMTP connections when use SMTP550DISCONNECT, Is correct my theory?

Hi,

I have a little problem and I want that you confirm me my suspects or  
say me if I'm wrong.

When I use the SMTP550DISCONNECT="" option, the opened SMTP sessions  
always are more than when I don't use it.

My theory about that is:

- If I don't use it, qmail send 4.x.x or 5.x.x message, remote client  
receive it, close the socket and send a notification to qmail. Then,  
as TCP transaction has finished correctly, local SMTP socket is close  
definitely.

- If I use SMTP550DISCONNECT, qmail drop connection without receive  
any data more from client, so, my SO keep the local SMTP socket in  
TIME_WAIT during 60 seconds (RHEL 5.5).

Am I correct?

Regards,
Spamis