This the second lookup table introduced with postfix-2.12-20140618.
Wietse
As the name suggests, the "pipeline" table implements a pipeline
of lookup tables. The name of the table specifies the pipeline as
a sequence of tables. For example, the following prevents SMTP mail
to system accounts that have "nologin" as their login shell:
/etc/postfix/main.cf:
local_recipient_maps =
pipeline:!unix:passwd.byname!pcre:/etc/postfix/no-nologin.pcre
alias_maps
/etc/postfix/no-nologin.pcre:
!/nologin/ whatever
The ASCII character after "pipeline:" will be used as the separator
between the lookup tables that follow (do not use space, ",", ":"
or non-ASCII).
Each "pipeline:" query is given to the first table. Each table
lookup result becomes the query for the next table in the pipeline,
and the last table produces the final result. When any table lookup
produces no result, the entire pipeline produces no result.
Some future version may support the form pipeline:/path/to/file,
to load the list of lookup tables, one per line, from a textfile.
