About setup and established Questions and log tracking Program

[Vahric MUHTARYAN]

Hi Everybody , 

I'm newly using ipfw ... I have some quesitions about ipfw configuration
.. 

I'm maked changes on defult configuration in rc.firewall for simple type
but I don't understand something ... 


	  # Allow TCP through if setup succeeded
        ${fwcmd} add pass tcp from any to any established

        # Allow setup of incoming email
        ${fwcmd} add pass tcp from any to ${ip} 25 setup


I checked man page of ipfw ; setup matches packets have SYN bit or not
.... 
Upper rule is accepting setuped connections that ok ( please correct if
I wrong ) 

	Question is Why I need to set setup options on secound rule ...
I mean I must to open 25 ( smtp port ) to all What is the setup option
role ... 

Vahric