Difficulties with Sonicwall TZ170 –> SMTP

Hello all,
I have some difficulties with setting Firewall for port 25.
Network schema:
router -> firewall -> server
Router: WAN: Fixed IP 84.xxx.xxx.xxx
LAN: 192.168.2.2
Firewall: WAN: 192.168.2.1 (NAT)
LAN: 192.168.1.254

Problem is regarding receiving email from my ISP on port 25(Exchange Server). I thing that there is a problem with firewall setting but even if I set “Allow ALL from WAN to LAN”
I can not telnet on port 25. Have you any suggestion how to overcome this?
Many thanks.Crane