Further Processing: $:address
The address part of the triple is intended for use in
the command line of the delivery agent and in the
RCPT command in an SMTP connection. For either use,
that address is rewritten by rule set 2 (if there is
one), the R=
equate of the delivery agent, and the final
rule set 4, as
illustrated in Figure 19-5. This means that the address part can be in
focused form because the focus is later removed by
the final
rule
set 4. But the address part
must be a single username (no
host) for some local delivery agents.
The rewritten result is stored for use when a delivery
agent’s $u
in
A=
(A= on page 738) argument is
expanded. For example, for the local
delivery agent,
the rewritten result is the username as it will be
given to /bin/mail for local
delivery.
Figure 19-5. The flow of $:address through rule sets
The rewritten result is also given to a remote site
during the exchange of mail using the SMTP protocol.
The local machine tells the remote machine the name
of the recipient by saying RCPT To:
followed by the rewritten
address portion of the triple.
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