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Leave Enable checked.
Select your Internet connection in Destination Address.
Enter the translated port of the packet. If you leave this blank, then the port will be
unchanged. You cannot translate the port for IP protocols or ICMP messages. You
should normally set this field to the port of the service on your internal server.
You cannot translate the port if Services is set to a predefined service. This is because a
predefined service may contain multiple protocols, so a single port definition is not well
defined.
Click Show Definitions next to Ports.
Select E-Mail from the Services pull-down list.
Enter your internal email server’s IP address in To Destination Address.
Click Finish.
Configure mail clients on the Internet with the SnapGear unit’s Internet IP address as the
server to use for sending (SMTP) and receiving (POP3 or IMAP) mail. If your SnapGear
unit has a dynamic Internet IP address, consider using a dynamic DNS server; see
Dynamic DNS in the DNS section of the chapter entitled Network Setup.
Source NAT
Source NAT alters the source address of packets received by the SnapGear unit. This is
typically used for fine tuning the SnapGear unit’s masquerading behavior.
See the Masquerading section later in this chapter for information on altering the basic
masquerading relationships between your SnapGear unit’s interfaces.
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