User manual

RaQ 3 Server Management
51
Email relaying
Simple Mail Transfer Protocol (SMTP) service is different from Post
Office Protocol (POP), telnet and file transfer protocol (FTP) services in
that SMTP does not try to authenticate a user when an SMTP
connection is made. Every email server on the Internet has to be able to
deliver email to you, so the email servers must be able to connect freely
to send the email. The Cobalt server accepts email if the recipient has a
user account or an alias email account, or if the sending host (your
client PC) is trusted to relay outgoing emails to another domain. These
trusts are defined by host or domain names, as well as by IP addresses
and networks. A network is a range of IP addresses; a network can be as
small as one IP address, but that is not very practical.
!
Caution: Some users advise you to open relay to all com, edu,
net and other top-level domain addresses. This is BAD
ADVICE. Doing so allows hosts belonging to com, edu, net and
others to relay email through your Cobalt server; this relayed
mail is known as spam mail.
Spam mail can appear as though it originated from your server
and as a result, others may blacklist your server as a known
spam site. If your server is blacklisted, many mail servers will
not relay your email and your customers will not receive any
email messages.
If you have users who access your server through the Internet, ask your
Internet Service Provider (ISP) which networks are used by their remote
access (dial-up) equipment. If the ISP says the network 209.43.21.5/24
and 209.43.66.5/16, add “209.43.21” and “209.43.66” to the “Relay
email from these hosts/domains” field of the Email Parameters menu. If
your ISP gives you a list of 30 networks used by 30 points-of-presence
(POPs) (which are regional ISP offices) across the country and your
clients can dial in from any of them, then you must trust all 30 networks
or these users cannot send email through your RaQ 3.