Technical data

SHOW MX_RECORD
Host address Host name
18.18.100.10 SWAN.WEBBED.FEET.COM
Displays, in order of preference, the routing hops to reach host SWAN if an
attempt fails. The local host tries to route through:
1.
WATER.PIPIT.WEBBED.FEET.COM
2. bd-gw.purple.martin.com
3. great.horned.owl.com
4. bird.food.seeds.worms.com
Both the alternate gateway and the zone affect how SMTP determines where
to relay nonlocal mail.
MX records tell mailers where to relay mail that is destined for a given host.
In the display:
• The Gate name field tells where to relay the mail.
• The Gate address field gives the gateway’s IP address.
• The
Preference field gives each MX record a precedence. A lower
preference number means a higher precedence.
2.
TCPIP> SHOW MX_RECORD CROW.COM
BIND MX database
Server: 18.18.218.10 WATER.PIPIT.WEBBED.FEET.COM
Gate address Preference Gate name
159.228.12.253 1 cawcaw.crow.com
159.228.12.254 2 scare.crow.com
TCPIP>
Displays the MX record for destination host crow.com . In the display:
• The Gate name field tells where to relay the mail.
• The Gate address field gives the gateway’s IP address.
• The Preference field gives each MX record a precedence. A lower
preference number means higher precedence.
In this example, the local host name is WATER, the alternate gateway is
scare.crow.com , and the zone is crow.com . The first preference for delivering
mail to crow.com is to send to cawcaw.crow.com .
If you have not defined an alternate gateway, SMTP tries to relay the mail
to scare.crow at IP address 158.228.12.253. It uses the MX records to
determine the host to which to relay mail. SMTP tries to relay the mail to
each gateway host, in order of preference, until it either successfully transfers
the mail or runs out of MX records to try. If there is no alternate gateway,
the zone is not used.
If you have defined an alternate gateway, SMTP goes through the list of
MX records, but it does not automatically try to relay the mail directly to
the gateway. SMTP checks whether the gateway host name is outside or
inside the SMTP zone (as defined with SET SMTP CONFIGURATION). If the
gateway is inside the SMTP zone, SMTP tries to relay the mail directly to the
gateway host. If the gateway is outside the zone, SMTP sends the mail to the
alternate gateway.
Command Descriptions 2–175