IMail Server 7.1 User's Guide - Setting Up IMail Server as a Mail Gateway

Setting Up IMail Server as a Mail Gateway

You can set up IMail Server to function as a mail gateway for another mail server. This means that mail for the other server is sent and received through the IMail Server. Often, people will set up a mail gateway because their mail server uses a dial-up connection and is not always connected to the Internet.

If you want IMail Server to be a gateway for another mail server, the other server must be running SMTP.

To set up IMail Server as a gateway for another mail server, check the following:

The mail domain (for example, domain2.com) for which IMail Server is a gateway does not appear in IMail Server.
User accounts for the mail domain are on the other server.
The MX record for the mail domain must point to the IMail Server host. Thus, mail addressed to that domain will come to the IMail Server host. (This MX record is in the DNS used by the other mail server.)
The IMail Server host must be able to resolve the domain name to the IP address of the other SMTP server. This is accomplished by making an entry for the domain name and IP in the hosts file
(\winnt\system32\drivers\etc\hosts) on the IMail Server host.
This works because IMail Server checks the hosts file and IP information before checking the DNS server. IMail Server queues the mail until it is delivered to the other server, or until the Queue Timer setting multiplied by the Number of Tries has elapsed. (The Queue Timer and number of tries are set on the SMTP tab).
If you are using any of the "Relay Mail for" options on the SMTP Security tab, and want to relay outgoing mail for another mail server, the address of the other server must be added by using the "Addresses" button, and entering the remote IP's into the table.

The following example shows how you can set up IMail Server to accept mail for a domain (domain2.com) and forward all mail for this domain to another SMTP server. Assume the following:
Other mail domain name	domain2.com

Host name of other SMTP server:	other_SMTP_server
IP address of other SMTP server:	156.21.50.240
 
Host name of IMail Server:	my_imail_machine
IP address of IMail Server:	156.21.50.10
 
When Windows NT/2000 looks up a domain name, it first searches the \winnt\system32\drivers\etc\hosts file. So, in the hosts file point the domain name to the IP address of the other SMTP server:

156.21.50.240 domain2.com

You can use the ETRN command to manually retrieve mail from the ISP's mail server. See "Using ETRN to Retrieve Mail" for more information.

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