with pix v6.x, a nat/global or static is a must do before the pix will forward the packet between the interfaces.
below is the sample codes with the scenario you posted:
global (outside) 1 interface
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
static (inside,outside) tcp interface 80 80 netmask 255.255.255.255
static (inside,outside) tcp interface 443 443 netmask 255.255.255.255
static (inside,outside) tcp interface 25 25 netmask 255.255.255.255
static (inside,outside) tcp interface 110 110 netmask 255.255.255.255
access-list 111 permit tcp any interface outside eq 80
access-list 111 permit tcp any interface outside eq 443
access-list 111 permit tcp any interface outside eq 25
access-list 111 permit tcp any interface outside eq 110
access-group 111 in interface outside
for ping to work from inside to outside only:
access-list 111 permit icmp any any echo-reply
access-list 111 permit icmp any any unreachable
access-list 111 permit icmp any any time-exceeded
for ping to work from both direction, i.e. from inside to outside, and from outside to inside
access-list 111 permit 111 permit icmp any any
please note that i'm assuming that you've got only 1 public ip, and that's why the static statements above are with port forwarding. alternatively, if you have more than 1 public ip, then the static statements should be:
static (inside,outside) netmask 255.255.255.255
access-list 111 permit tcp any eq 80
access-group 111 in interface outside
finally, another quick comment is that pix v7 doesn't support pix 501 and 506/506e.
