HP-UX Mailing Services Administrator's Guide

Sendmail 8.13.3

New Features in Sendmail 8.13.3

Chapter 3 113

where, hostname specifies the canonical name to which the host will

fallback.

Mail message forwarded to that host name fails if hostname is an empty

string or is the name of a nonexistent host. You can also use macros to

represent the hostname. Sendmail expands these macros before

connecting to the remote host. If the hostname that you specify for the

FallBackSmartHost option exists in the $=w class, Sendmail silently

ignores the hostname.

The FallBackSmartHost option is also useful for unreliable

FallbackMXhost servers. When the FallbackMXhost server goes down,

Sendmail uses the FallBackSmartHost option and thus the flow of mail

messages does not stop.

You must be careful while using the FallBackSmartHost option because

if you specify this option from the command line, Sendmail can

relinquish its special privileges.

Socket Maps

Sendmail 8.13.3 contains a new socket map to query maps through

TCP/IP sockets.

The socket map uses a simple request or reply protocol over TCP or

UNIX

domain sockets to query an external server, which can be a third

party or a self-coded program. Neither the requests nor replies end with

a carriage return (CR) or line feed (LF). Both the requests and replies are

text based and encoded as net strings. A string "hello there" is

represented as follows:

11:hello there

The request consists of the database map name and the lookup key

separated by a space character, specified as follows:

The server responds with the following status indicator and the result (if

any):

The status indicator is one of the following upper case words:

OK Specifies that the key is found and the result contains

the looked-up value.