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New Member

SMTP Server : inbound and outbound NAT?

Hi all,

I work with a Cisco PIX 515E UR with 3 interfaces : Inside, DMZ and Outside.

In the DMZ, I have a SMTP Server.

I want first that any host on the outside can reach this server on the port 25.

I think using NAT:

static(dmz,outside) global_addr,local_addr

and then add a access rule:

access-list acl_out permit tcp any host global_addr eq smtp

acl_out is then applied in the access-group bound to the outside interface.

I think It was Ok with this configuration, but it doesn't work :(

From the outside, I try to telnet my SMTP server (with his public address) on the port 25, It doesn't work.

I have also a second problem... I want this SMTP server to go on the outside. Must I add a "nat(dmz) 1 0 0" command, and specify a global pool on the outside network or is the "static" command enough to assure inbound AND outbound traffic from and to my SMTP Server?

Thanks you by advance for your help.


New Member

Re: SMTP Server : inbound and outbound NAT?

Hello Khay,

Be sure to clear the xlate table after creating the static nat. "clear xlate"

What do you get when you try to telent through port 25. If you get ****22 or characters like this, then you need to disable fixup smtp or inspect smtp depending on the version you're running.

The static nat works bidirectionally, so you do not need to create another translation rule.

New Member

Re: SMTP Server : inbound and outbound NAT?

Hello Khay,

First of all placing Exchange Server in DMZ is not a good idea. I suspect you might beplacing OWA server or relay server in DMZ as a best practice, in such scenario's just allow smtp, https, http as well or incomming traffic. For outgoing from dmz to inside or outside yes, you need to nat them all or specific servers subnet. nat (dmz) 1 or any specifi IP


New Member

Re: SMTP Server : inbound and outbound NAT?


try to verify and delete the ip inspect for smtp protocol: only the version after the 7.x support the ESMTP protocol !!!

Best regards

New Member

Re: SMTP Server : inbound and outbound NAT?

the command for the ver. 6.x:

no fixup protocol smtp 25