sendmail, 4th Edition

DontProbeInterfaces

Don’t probe interfaces for $=w V8.9 and later

When sendmail first starts up, it probes all your network interfaces to see what hostname is assigned to each.^[383] For all that it finds in the up state, it adds that hostname to the class $=w ($=w on page 876), meaning that class will be considered a valid name for the local machine.

Sometimes, however, especially when supporting virtual hosts, sendmail should not consider all the interface hosts as local. Because there is no way to remove a name from a class, it is better to not have sendmail probe the interfaces in the first place. Then, you will be able to manually add (or add via your /etc/mail/local-host-names file;^[384] see FEATURE(use_cw_file) on page 643) just the names you want into the class $=w.

You can disable sendmail’s initial scanning of interfaces for hostnames by declaring this DontProbeInterfaces option:

O DontProbeInterfaces=bool                      ← configuration file (V8.10 through
V8.11)
-ODontProbeInterfaces=bool                      ← command line (V8.10 through
V8.11)
define(`confDONT_PROBE_INTERFACES',`bool')      ← mc configuration (V8.10 through
V8.11)
O DontProbeInterfaces=string                    ← configuration file (V8.12 and
later)
-ODontProbeInterfaces=string                    ← command line (V8.12 and later)
define(`confDONT_PROBE_INTERFACES',`string')    ← mc configuration (V8.12 and
later)

The argument bool is of type Boolean. If it is missing, the default value is true—don’t probe interfaces at startup for hostnames. The argument string is of type String (for V8.12 ...