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.

^[6] 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). 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) to determine which network types are supported (if any appear in the list, support is included).