Cisco 2801 with Firewall and NAT

Hi,

I have installed a Cisco 2801 with firewall feature into my customer network. 2801 with 2 LAN interface. First FE0/0 connected to the internal LAN with IP 192.168.1.1/24 and FE0/1 connected to the SDSL with static IP (115.133.xxx.86/255.255.255.252). The firewall rules is Any-Any allow.

Before the deployment of Cisco 2801, the customer with wireless router can send mail to their mail server at external with port 25. But, after the Cisco 2801 deployment, the customer was unable to send mail via port 25. We have verify with the ISP, they only block port 25 from dynamic IP and not static IP. However, if we send mail via other port is ok.

Anyone can advise where went wrong.

TQ,