Beginning with V8.7 sendmail, configuration file options can use multicharacter option names. Prior to V8.7, only single characters were allowed. We describe the old form first, then the new.
The old form for an option command in the sendmail.cf file is:
OXargument prior to V8.7
Like all configuration commands, the uppercase letter O must begin the line. It is immediately followed (with no intervening space) by another single letter, which selects a specific option. Uppercase letters are distinct from lowercase for single-character option names (that is, X is different from x). Depending on the option selected, an argument might be required. There must be no intervening space between the single-character option name and its argument.
Single-character option names should be considered deprecated in favor of the more modern multicharacter option names.
Beginning with V8.7, option names can be single-character or multicharacter. A space is used to differentiate between single-character and multicharacter (long) names:
O LongName=argument beginning with V8.7 a space (not a tab)
Whenever the O configuration command is followed by a space (not a tab), everything following that space is taken as the declaration of a multicharacter option. Unlike single-letter option names, multicharacter names are interpreted by sendmail without regard to case. Therefore, the following three examples all produce the same effect:
O QueueDirectory=/var/spool/mqueue O queuedirectory=/var/spool/mqueue O QuEuEdIrEcToRy=/var/spool/mqueue
Optional space (not tab) characters can surround the = character:
O QueueDirectory = /var/spool/mqueue spaces, not tabs
Multicharacter names in the configuration file ought not be abbreviated or expressed in shorthand:
O QueueDirectory =/var/spool/mqueue good O QueueDir =/var/spool/mqueue bad, but allowed
Failure to use the full multicharacter name will cause sendmail to print spurious warnings every time it is run. The possible warnings are listed in Section 18.104.22.168.