Chapter 4. Your Internet Service Provider (ISP)
Some Important Notes on Service List D (Multidrop Mail)
Service list D is applied to configurations where the publication of DNS records is not practical either because your IP address
changes frequently or because it is non-routable. Because there is no published address receiving incoming network
connections, this configuration does not allow you to host a web page or FTP site using your SME Server V5 with ServiceLink.
In this case, e-mail is handled using a method called "multidrop", which involves temporarily storing all e-mail messages
addressed to your domain in a POP mailbox at your ISP until your server connects and fetches them. Your POP mailbox must be
large enough to hold the e-mail for your organization until it is fetched. If your primary ISP cannot supply this, you can use
another ISP for your e-mail hosting.
As e-mail messages are delivered into the POP mailbox at your ISP, some of the addressee information is removed. To determine
to whom the e-mail message is addressed, your server uses several heuristics. This works very well for normal person-to-person
e-mail. However, messages from mailing lists (and other sources where the user’s account name is not present in the headers)
cannot be delivered. Any e-mail that cannot be delivered will be returned to the sender. If the e-mail cannot be returned to
sender, it will be directed to the system administrator.
Some ISPs add a header to each e-mail message as it enters the POP mailbox to assist in determining the addressee. One
common header tag is: "X-Delivered-To". If your ISP does this, make note of the header tag used so that you can configure your
server to look for it (explained in a later section).
Because of the potential problems involved with delivery of e-mail to multidrop mailboxes, we strongly encourage you to
consider other means of mail delivery before resorting to using multidrop.
Terms used in ordering connectivity and services
ADSL (or DSL)
ADSL is a type of high-speed Internet access that uses regular phone lines and is available in many metropolitan areas.
Domain Name
This refers to the unique name attached to your organization on the Internet. For example, "tofu-dog.com" or "e-smith.com". If
you don’t have a domain name, your ISP can help you select one, ensure it is available, and register it.
DNS (Domain Name Service)
DNS, or Domain Name Service, refers to the software and protocols involved in translating domain names to IP addresses. Your
server provides DNS lookup services for your local network, and your ISP typically also provides you with the IP addresses of
DNS servers. These servers do not need to be configured into your server as the DNS server that is provided with your server
will correctly resolve all local and Internet names.
DNS: Publication of DNS Address Records
The publication of DNS address information allows other DNS servers to look up your domain information. Your ISP must
publish DNS address records associating the name of your web server ("www.domain.xxx"), FTP server ("ftp.domain.xxx") and
e-mail server ("mail.domain.xxx") with the IP address of your server.
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