[ILUG] etrn & ipchains

[gerdono at eircom.net]

I have configured a firewall using ipchains kernel 2.2.16
everything works except for my mail delivery. Mail Server is on another server and use ETRN deliver to eircom.
ETRN command is traversing the firewall no problem but returning mail only comes as far as the firewall machine and does not get back to Mail Server.
Mail Server is VPOP3 (NT Server) 
I think my problem is due to the messages been delivered on a different port ??
Anyone got any ideas or config something similar

regards ger donohue