FreeBSD 6.1 and 6.2 i386 firewall or NAT block web mail applications

Hi,
I need some help with FreeBSD firewall with NAT. I have made pppoe and
NAT working with both 6.1 release and 6.2 RC i386. All I want is to
forward port 443 to port 8843. I added a line in the OPEN portion in
the rc.firewall file:
${fwcmd} add fwd 127.0.0.1,8843 tcp from any to any 443 in keep-state
Now, when I type https://myserver's ip, it will forward to a proxy
server listening at 8843. This is good. But, in the local network,
nobody can access the yahoo and google mail.
I made another kernel with the options IPFIREWALL_DEFAULT_TO_ACCEPT.
When I ipfw, there is only one rule:
allow ip from any to any
This is good.
When I added a line
ipfw add fwd 127.0.0.1,8843 from any to any 443 in keep-state
again, it won't work with any web email applications.
I added a line like this
${fwcmd} add pass tcp from any to any 25 setup
Still it won't work.
pen at both 6.1 and 6.2 are not working. I remember it works only with
7.0-current.
I have only 3 options when I compile the kernel:
options IPFIREWALL
options IPFIREWALL_FORWARD
options IPDIVERT

in order to get pppoe to work, I added
options NETGRAPH
options NETGRAPH_PPPOE
options NETGRAPH_SOCKET

my rc.conf is like this
gateway_enable="YES"
hostname=...
ifconfig_ed0=...
ppp_enable="YES"
ppp_nat="YES"
ppp_profile="sympatico"
ppp_mode="ddial"
firewall_enable="YES"
firewall_type="OPEN"

By the way, I have made this mistake twice:
Comment out firewall_enable and firewall_type, the default rule is to
lock out any body. I could not access my remote server. I wish you
would not do this like me.
The best way is to have an options IPFIREWALL_DEFAULT_TO_ACCEPT. The
problem is : whenever you add some rule, it will block web mails!