Cristiano Otto Von Trompczynski
The optional virtual table specifies redirections for local and non-local recipients or domains.
The redirections are used by the cleanup(8) daemon. The redirections are recursive.
The virtual redirection is applied only to the recipient envelope address, and does not affect
message headers. Think Sendmail rule set S0, if you like. Use canonical(5) mapping to rewrite
header and envelope addresses in general.
The file serves as input to the postmap(1) command. The result, an indexed file in dbm or db
format, is used for fast searching by the mail system. After an update it may take a minute or
so before the change becomes visible.