What is IP Binding for Domain Groups and how to use it?
You can use IP binding for domain groups if your computer has more
than one IP address, and it listens on all of them (value of Options - Server Options
- IP Binding - Listen on the Following IP Addresses is All Available).
Use of IP Binding for domain groups makes your server behave as
if each domain group was completely independent from each other, like each domain
group was running its own virtual server, with its own SMTP greeting, SMTP EHLO/HELO
fully qualified domain name, and it's own bounce-from email address.
Let's assume you have two IP addresses on your computer, 111.111.111.111
and 222.222.222.222, also, you want to serve two domains,
which are not related to each other (under "not related" we mean, that they do not
need to share users, they are not in the same domain group, they are not aliased
to each other): one.com and two.com.
You have created two domain groups on your server: Domain Group One,
with the domain name one.com, and Domain Group Two, with the domain
name two.com.
Let's consider the case when we are not using IP Binding for Domain Groups
(Edit Domain Group box we will see if we select a domain group, and click
Edit button on the Domains and Users page, the settings of Bind To
field is either Any Available, or the IP Binding box is
completely disabled - it will happen if a Listen on the Following IP Addresses box
on the Server Options box is anything but All Available).
Let's assume, the setting of the Local Host box on the Options - Server Options
- General box is mail.one.com, and the value of SMTP Greeting is
blank (empty).
Try to telnet to the port 25 of your server, using all possible IP addresses, go
to the DOS prompt, and type:
telnet 111.111.111.111 25
and, later:
telnet 222.222.222.222 25
We will see the similar greeting from the server, which will look like:
220 mail.one.com ArGoSoft Mail Server SMTP Module
v.1.0.4.9 at Sun, 25 May 2008 01:04:05 GMT
Pay attention to the mail.one.com. This is the value comes from Server Options
- General box, where it is specified as Local Host.
Now, let's enable IP Binding for domain groups. Let's select
Domain Group One, on the Domains and Users page, click Edit,
and in the Bind To box select 111.111.111.111, in the
Local Host box type mail.one.com, leave Bounces From
and SMTP Greeting boxes blank for now. If they are blank, then values
will be taken from general settings, either from Server Options,
or Services...
Do the same with the Domain Group Two, select 222.222.222.222
in the Bind To box, and type mail.two.com in the Local
Host box.
Now, we can see results. Telnet to 111.111.111.111, port 25. Greeting will look
exactly the same:
220 mail.one.com ArGoSoft Mail Server SMTP Module v.1.0.4.9 at Sun, 25 May 2008
01:04:05 GMT
But, if we telnet to 222.222.222.222, that's what we will see:
220 mail.two.com ArGoSoft Mail Server SMTP Module v.1.0.4.9 at
Sun, 25 May 2008 01:04:05 GMT
This time, mail.one.com and mail.two.com came
from Edit Domain Group boxes. For the first domain we see the same
value (mail.one.com), because that's what we have entered in the Local Host
box, and for the second domain we see mail.two.com, from the similar
location!
That's IP Binding for domain groups in action, and it does not stop just here. If
you specify SMTP greeting for each domain, they will be selected according
the the connecting IP address, and (it is important) if we go back
to Options - Server Options - IP Binding box, and select Same as Incoming
in the For Outgoing Mail... box, then the server will use mail.two.com
with SMTP EHLO/HELO command when delivering to exchangers, if the message being
relayed was sent via 222.222.222.222, and mail.one.com, if mail
was received at 111.111.111.111. It means, it will identify itself as a server,
serving the particular domain.
Usually, it is not required that the server identifies itself as one from some particular
domain, but, if it does, it adds your emails more credibility. It also may be important
for owners of domains you are hosting on your server to see the name of their server
in SMTP greetings.
Starting from v1.0.5.0, you can enable SMTP connections to specific IP addresses
from the Web Intrface, and take advantage of the IP binding feature
of the mail server.
Starting from v1.0.5.0 web interface uses remoting services to communicate with
the mail server. For sending mail out, it uses SMTP protocol. You can associate
domain names of logged in users with specific addresses of SMTP servers, which will
be used for sending mail out when logged in user has a matching domain in his/her
user name.
This document describes how to associate
domain names with SMTP servers when using web interface.
If you have further questions, please submit it from our
Support Page.
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