NAT mail to new internal smart host

[networking]

Hi all.

I have a PIX 515E. I have an old smart host server that I am retiring with an ip address of 172.17.2.50. I have built a new smart host server with an ip of 172.17.5.2.

My current working config on the pix is the following:

access-list 30 permit tcp any host 62.120.56.37 eq smtp

static (inside,outside) tcp 62.120.56.37 smtp 172.17.2.50 smtp netmask 255.255.255.255 0 0

nat (inside) 2 172.17.2.50 255.255.255.255 0 0

When I tried testing the new server, I just replaced the ip address of 172.17.2.50 with 172.17.5.3. Our mail flowed for about 10 email messages but then stopped.

Am I missing something?

[srue]

no static (inside,outside) tcp 62.120.56.37 smtp 172.17.2.50 smtp netmask 255.255.255.255 0 0

static (inside,outside) tcp 62.120.56.37 smtp 172.17.5.2 smtp netmask 255.255.255.255 0 0

also, what is the purpose of the nat (inside) 2 statement..where is the 'global (outside) 2' statement?