It's recommended for people to enable port forwarding, not disable it. Passive DCC will only work with clients who are setup to allow incoming connections. Finally, you should not use Normal Lookup behind a router, as mIRC will be reporting the wrong IP address. Changing it to Server won't affect your sending with passive DCC, but it will make $ip return the correct value.
I cannot disagree with you :-) However, it works for me. Port forwarding doesn't.