This can also be done in combination with
direct delivery if you have both your own domain and mailboxes under shared domains.
Configuration of Fetchmail is explained in the ???Configuring Mail Clients??? section of this
chapter.
Configuring DNS for Direct Delivery
For direct delivery to function, the SMTP service (TCP port 25) must be accessible to the outside
world through a fixed name in DNS. This name will be in the form of an A (Address) record. A
records allow DNS resolver processes to determine the IP address associated with a specific name
and are used by most of the common protocols on the Internet. A typical DNS A record looks
something like this:
bigserver.example.org IN A 10.0.12.16
The first parameter, bigserver.example.org, is the label, and the second parameter is the class
(IN for Internet, which is where most DNS records are found). The A indicates the type, and the
final parameter is the IP address associated with the label.
Once you have your A record, you can direct mail to your server using an MX (Mail eXchanger)
record. The A and MX records do not need to be part of the same domain, which allows for much
greater flexibility. Here is a sample MX record:
widgets.test. IN MX 0 bigserver.example.org.
This MX record indicates that mail for any address@widgets.
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