sendmail, 4th Edition

NET...

Define for network support Tune with confENVDEF

Beginning with V8.10, sendmail is designed to support six kinds of network sockets, as listed in Table 3-10. Currently, NETNS and NETX25 are accepted but not implemented.

Table 3-10. Define for network support

Define	Description
[a]
NETINET	A TCP/IP-based network (IPv4)
NETINET6	An IPv6-based network
NETISO	An ISO 8022 network
NETNS	A Xerox NS protocol network (tentative)
NETUNIX	A Unix domain network
NETX25	A CCITTN[a] X.25 network (tentative)
[a] a International Telephone Consultative Committee.

Stubs are included in the source code for any programmer who is interested in implementing NETNS or NETX25. In general, the others are already declared appropriately for your system. Should you desire to change one, you can do so in your Build m4 file. The following, for example, removes support for IPv4 from sendmail:

APPENDDEF(`confENVDEF', `-DNETINET=0')

Defining network support only causes the code for that network to be included in sendmail. The network serviced by a particular invocation of sendmail is selected with the Family parameter of the DaemonPortOptions option (DaemonPortOptions on page 993). In the absence of an option declaration, IPv4 (for NETINET) is used as the default.

If you are running a precompiled sendmail binary, you can use the -d0.1 debugging command-line switch (-d0.1 on page 542) to determine which network types are supported (if any appear in the list, support is included).