ipfw and smtp port rewriting

[Oleksandr Samoylyk]

Hello freebsd-ipfw,

I'd like to make smtp port rewriting for any destination by means of ipfw.

With iptables I just used this rule in order to achieve this functionality:

iptables -t nat -A PREROUTING -i ppp+ -p tcp --dport 2525 -j DNAT 
--to-destination :25

Reading man ipfw and playing a bit with rules I composed this rule, 
which doesn't however work:

ipfw add fwd any,2525 tcp from any to any 25 via ${tun}

How to achieve the same functionality as in iptables for smtp port 
rewriting for any destination?

Thanks!

-- 
  Oleksandr Samoylyk
  OVS-RIPE