When a mail message arrives that
includes an ORCPT parameter for the ESMTP RCPT command (see RFC1891),
sendmail needs to save that
parameter's information separately from the RCPT
recipient address:
RCPT TO:<gw@wash.dc.gov> ORCPT=rfc822;gw@wash.dc.gov
recipient address parameter's information
Not all sites understand DSN. If sendmail
forwards the message to such a site, it needs to omit the ORCPT
parameter. Consequently, sendmail must not store
that parameter with the RCPT address.
The Q line is used to separately store the ORCPT
parameter information:
Qtype;addr
The
type;addr
is defined by RFC1891. The sendmail program
checks the syntax of addr when that
information is received but otherwise merely stores
type;addr as is
in the Q line.
There must be only a single Q line for each
recipient R line, and each such
Q line must precede its corresponding
R line.
