-o
The database map is optional V8.1 and later
Ordinarily, in the case of types that employ disk
files, sendmail will complain
if a specified file cannot be opened for reading. If
the presence of a database file is optional (as it
can be on certain machines), the -o
switch should be used
to tell sendmail that the
database is optional. Note that if a database is
optional and cannot be opened, all lookups will
silently fail for rules that use that
database.
Also note that for network-based types of database
maps, this -o
switch can be used to cause failed initializations
to be ignored. If a database map is used during the
processing of a message, and if a lookup fails in
the absence of a -o
switch, the message (or SMTP
request) will be rejected with a temporary
failure.
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