Mail stuck in Postfix queue

Hi,

I wrote before about no confirmation being sent but I got past that.

When I sent an email to the tmda user I get a confirmation request back.
When I answer that I get another email back saying my confirmation  
has been accepted.

But the email is not delivered to the tmda users?

If I do a "postqueue -p" I see the email in the queue.

If I send another email the first one is delivered but the second  
stays in the que?

If I wait about 45 minutes the email stuck in the que is delivered.

This seems like some sort of Postfix problem and not really tmda but  
does anyone
have any ideas what could cause this?

Thanks.

Pat.

Platform Xserver, OS X 10.4.10