Options are declared in the configuration file by beginning a line
with the letter
OQ/var/spool/mqueue ← single-character name (prior to V8.7)
Prior to V8.7 sendmail, option names could only
be a single character. The short (single-character) name of the
Q) immediately follows the
O with no intervening space. The value assigned to
a single-character option immediately follows the option letter with
no intervening space.
Beginning with V8.7 sendmail, option names can be composed of multiple characters:
O QueueDirectory=/var/spool/mqueue ← multicharacter name (beginning with V8.7) ↑exactly one space
To use multicharacter names, you must separate the name (here,
QueueDirectory) from the
command with exactly one space character.
The value assigned to the multicharacter option follows an equal
sign. The equal sign can be surrounded by optional spaces.
Some options have both a single- and a multicharacter name, in which case the two names are equivalent, and the modern multicharacter name is preferred:
OQ/var/spool/mqueue ← define location of queue directory O QueueDirectory=/var/spool/mqueue← the same and preferred
The short name is retained so that old configuration files will still work with newer versions of sendmail. They should, however, be considered deprecated, and support for them might disappear in future releases of sendmail. Most options (especially the newer ones) only have multicharacter names:
O ServiceSwitchFile=/etc/service.switch ← only multicharacter ...