Three domain / Three Public IP address / Three Physical Servers

[justanotherdayintheoffice]

Good day Everyone!

Please refer 1st to the attached diagram.

We are currently trying to find a way as to how we can route emails sent from sampleone.com to sampletwo.com without leaving the local network. We are doing this kind of setup to save bandwidth.

And since we have 3 public ip address, from my understanding is that in the firewall, we are going to NAT those three public ip addresses to ironport’s ip address and specify the accept incoming mail for the three domains. So my question is this, during an outgoing mail, how would the ironport know what public ip address is associated with a given domain? How would the firewall know that this domain/private ip address is associated with this public ip address?

Thanks

-karl

[Andreas Mueller]

Hello Karl,

basically you could set up three SMTP routes for the three domains, and use the internal  IP address of the servers as destinations.

GUI: network->SMTP Routes

CLI: smtproutes

smtproutes:

sampleone.com 192.168.1.10

sampletwo.com 192.168.1.20

samplethree.com 192.168.1.30

The routes are direction independend, means they will work for inbound and outbound alike.

BTW, a second approach would be using an internal DNS server which has the internal IP addresses for each of these daomains.

Hope that helps,

Andreas

[justanotherdayintheoffice]

Hi Andreas,

So what you are saying is that we setup SMTP Routes like the one below:

Receiving Domain                    Destination Hosts

sampleone.com                       192.168.1.10

sampletwo.com                       192.168.1.20

samplethree.com                     192.168.1.30

And if joe@sampleone.com sent an email to jane@sampletwo.com, the email address will be from:

MailServerOne(sampleone.com) - Ironport - MailServerTwo(sampletwo.com). And that the email will not go out to the internet anymore and then comeback again?

PS

We have developed a virtual lab but have not tried this on an actual three domain, 3 physical server, 3 public ip address setup.

[Andreas Mueller]

Hello Karl,

that is correct, before delivering a message, AsyncOS checks the SMTP route list, if an entry exists for the domain in the envelope recipient's address, that destination (which can be an IP or hostname) will be used, otherwise the IronPort will perform an MX lookup as usual. So if you have such a route installed, any mail to that domain will not be routed trough the Internet (public MX record).

One addition to the SMTP route syntax, just in case:

example.com  matches recipient adresses like user@example.com

If there are subdomains as well, you'd need another entry for that:

.example.com will match anything like user@host1.example.com, sales.host.example.com, etc. The leading period stands for any subdomains or multiple subdomains. Note that this will not match user@example.com, for that the entry without the period is still required.

Also, SMTP routes can point to multiple addresses (comma separated), and different ports than 25. Just to let you know.

Regards,

Andreas

[justanotherdayintheoffice]

This answer is correct. SMTP Route solves this.

Thanks Andreas.