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Understanding SMTP Mail Routing
Introduction
Performing a DNS
lookup
Example of
performing a DNS
lookup
IBM Proventia Network Mail Security System Getting Started Guide, Version 1.6
Before you set up and configure the appliance, you should understand
the basics of using SMTP, which will help you in determining where to
place the appliance on your network.
Every domain has a domain name server (DNS) that handles its requests,
and a System Administrator who maintains the records in that DNS.
These records are used to determine mail routing to and from the
Internet. You can easily check what servers are responsible for your
domain by performing an nslookup on the MX DNS records for that
domain.
The following example shows how to check the MX DNS records for the
domain:
iss.net
Open a command prompt, and then enter the following:
nslookup
The output would look something like the following:
Default Server: dns.server
Address: x.x.x.x
Now enter the following commands (these commands set the DNS query
to look up responsible mail servers for the iss.net domain):
set q=mx
iss.net
The output would look something like the following:
Server: dns.server
Address: x.x.x.x
iss.net MX preference = 5, mail exchanger =
atla-mx1.iss.net
iss.net MX preference = 10, mail exchanger =
colo-mx1.iss.net
iss.net MX preference = 10, mail exchanger =
sfld-mx1.iss.net
Understanding SMTP Mail Routing
13
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