ISA SERVER 2004 is blocking internal FTP traffic

Dear All,

I am having a problem with our internal FTP traffic. This is how every thing is setup.

Currently we are using watchguard firewall and we are using 1to1 Nat on DMZ interface which connects to ISA server 2004. We are publishing webmail,Mobile active sync and FTP through ISA server. Now every thing works fine external user can connect to FTP site no problem. But for internal user ISA server is deniying with no rule.

Our ISA server got 2003 windows and its got two interfaces internal and external.

Thing i don’t understand is why its deniying the internal traffic with no rule.

Please let me know if you require further details.

Thanks

Umar