Problems using secondary IP address for SMTP virtual server

18 May 2006 5:36 AM

Allyn

I am working on a network that was initially set up years ago using a
randomly chosen non-private IP network block, and they are not willing to
change any time soon. This company has a problem delivering email to a couple
other companies, because whatever spam filtering the remote company is using
apparently does not like to see this company's internal IP space in the
header as it doesn't belong to this company. The messages end up getting
rejected.

Trying to keep the network topology simple, I installed a secondary IP
address (172.16.3.1) on the adapter with the nonpublic IP address
(220.220.220.29), and set up a route on the firewall, so that packets can
reach the 172.16.3.1 address via 220.220.220.29. I have confirmed this works
- on the mail gateway in the firewall's DMZ, I can reach the 172.16.3.1.

The problem: I configured the SMTP default virtual server as using
172.16.3.1. However, the IP address shows up on the outside as
220.220.220.29. The only way I have been able to make this work is by binding
220.220.220.29 to the second adapter and installing a router, but I'd prefer
not to do this. Is there some way to make the SMTP default virtual server use
the private IP?

Thank you.

19 May 2006 12:28 AM

Bharat Suneja [MVP]

http://www.microsoft.com/technet/itsolutions/msit/operations/smtpggatewaysnote.mspx
Note that binding an SMTP virtual server to IP addresses affects only
inbound SMTP connections. The source IP address of the outbound SMTP
connections from the gateway server will be determined by the IP address
layer of the sending host. For example, if the gateway has two IP addresses,
172.16.x.1 and 10.x.x.1, and wants to communicate with the remote host
10.x.x.2, the source IP address of the SMTP connection will be 10.x.x.1,
regardless of which SMTP virtual server initiated the outbound connection.

*Possibly* one way of getting around this may be to setup static routes on
your servers for the destination networks - haven't tested this, so not
quite sure if it'll work.

--
Bharat Suneja
MVP - Exchange
www.zenprise.com
NEW blog location:
www.exchangepedia.com/blog
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Show quote

"Allyn" <Al***@discussions.microsoft.com> wrote in message
news:B16903FF-600C-4FD4-9AEB-8C5AEB89EE95@microsoft.com...
>I am working on a network that was initially set up years ago using a
> randomly chosen non-private IP network block, and they are not willing to
> change any time soon. This company has a problem delivering email to a
> couple
> other companies, because whatever spam filtering the remote company is
> using
> apparently does not like to see this company's internal IP space in the
> header as it doesn't belong to this company. The messages end up getting
> rejected.
>
> Trying to keep the network topology simple, I installed a secondary IP
> address (172.16.3.1) on the adapter with the nonpublic IP address
> (220.220.220.29), and set up a route on the firewall, so that packets can
> reach the 172.16.3.1 address via 220.220.220.29. I have confirmed this
> works
> - on the mail gateway in the firewall's DMZ, I can reach the 172.16.3.1.
>
> The problem: I configured the SMTP default virtual server as using
> 172.16.3.1. However, the IP address shows up on the outside as
> 220.220.220.29. The only way I have been able to make this work is by
> binding
> 220.220.220.29 to the second adapter and installing a router, but I'd
> prefer
> not to do this. Is there some way to make the SMTP default virtual server
> use
> the private IP?
>
> Thank you.