Technical data

Configuring and Managing SMTP
17.6 Configuring SMTP AntiSPAM
If a client IP address matches one in the Good-Clients list, the message is
accepted; the SMTP server does not check the RBLs.
17.6.5.1 Using Other RBL Lists
Other lists serve similar functions to the RBL list. For example:
• MAPS Dial-up User List — A list of IP addresses that participating ISPs have
allocated to them.
If you want to include a check against this list, add
dul.maps.vix.com to the
RBL list.
Even when SMTP is set up to reject all incoming SMTP connections from
dial-up IP addresses, mail can still be received from someone who is dialed up
to an Internet Service Provider (ISP). This is because they send their SMTP
mail to their ISP’s mail servers, and the ISP mail server connects to your
mail server. The IP address of the ISP’s mail server is not in an RBL, so this
connection will not be rejected.
This RBL list only prevents routing of e-mail from a dialup IP address directly
to your host.
You can allow your own dialup users to connect directly to your hosts without
being rejected. If your dial-up addresses have been included in an RBL, you
can exclude them from the RBL check by adding the IP addresses to the
Good-Clients list.
For more information about MAPS list, visit the following web site:
http://maps.vix.com
• Open Relay Behavior modification (ORBS) list — A list of SMTP servers that
are known to permit third-party relay.
To include this list, add
relays.orbs.org to the RBLs list in SMTP.CONFIG.
Caution
If you include relays.orbs.org in the RBLs list, you will not receive mail
from any host IP address in the ORBS list. This could prevent legitimate
mail from coming in.
For more information about the ORBS list, visit the following web site:
http://www.orbs.org
17.6.6 Translating Client IP Addresses
You can configure SMTP to translate the client’s IP address to a host name,
and to disconnect the link if no host name exists. To enable this feature, set
the Reject-Unbacktranslatable-IP option in SMTP.CONFIG. Translation is not
performed if the SMTP client’s IP address matches an entry in the Good-Clients
list.
Configuring and Managing SMTP 17–23