Technical data

Configuring and Managing SMTP
17.6 Configuring SMTP AntiSPAM
17.6.3.2 Processing DNS Entries in the Good-Clients List
The SMTP server uses the Good-Clients list to match the IP addresses of SMTP
clients. Therefore, entries are stored internally as IP addresses. DNS hostname
and MX domain entries are stored as IP addresses, determined by the following
process:
1. An entry that is not apparently an IP address or IP network is assumed to be
a DNS host name, and the matching IP address is stored in the list.
2. For an entry that cannot be resolved as a DNS host name, the SMTP server
looks for MX records.
For configurations where the generic mail server name does not have an
associated DNS host name, the SMTP server uses the MX records, which specify
mail relay hosts. The following example demonstrates this configuration:
TCPIP> show host relay.abc.com
%TCPIP-W-NORECORD, information not found
-RMS-E-RNF, record not found
TCPIP> show mx relay.abc.com
BIND MX database
Server: 1.2.3.4 host.abc.com
Gate address Preference Gate name
1.3.4.5 100 mail11.abc.com
1.3.5.6 100 mail13.abc.com
2.4.5.6 200 mail2.abc.com
2.4.5.7 200 mail1.abc.com
3.4.5.6 300 mail21.abc.com
3.4.6.7 300 mail12.abc.com
To include the addresses listed as MX gateways in this example, enter
relay.abc.com in the Good-Clients list.
17.6.3.3 Mail Relay to MX Gateways
You can configure the SMTP server to relay mail from an unknown SMTP client
to a domain that does not match the entries Relay-Zones but that has an MX
record naming the local host as an MX gateway. To enable this feature, set the
Relay-Based-On-Mx option to TRUE in SMTP.CONFIG.
For example, the Relay-Zones list is not specified on example host
VMShost.abc.com . When an unknown host tries to relay mail to podunk.def.com
through VMShost, and the Relay-Based-On-Mx option is enabled, the SMTP
server on VMShost searches for MX records for podunk.def.com . If one of
PODUNK’s MX records lists VMShost as the MX gateway, the relay is accepted,
even though the SMTP client is unknown and the RCTP TO address did not
match the Relay-Zones list.
17.6.3.4 Specifying the Relay-Zones List
The Relay-Zones list specifies the domains to which the SMTP server will relay
mail from unknown SMTP clients. Do not use wildcards in the entries in this list;
wildcarding is implicit (that is,
*.domain is implied). For example:
Relay-Zones: def.com,
abc.com,
company.com
17–20 Configuring and Managing SMTP