Bill Cole:
> Also, the setting "smtpd_delay_open_until_valid_rcpt = no" assures that
> the queue ID is known at RCPT time, making it possible for Postfix to
> provide it to milters as the default setting says it will.
This is not the default because it can increase queue activity by
an order of magnitude or more, at least for servers that reject the
majority of all mail delivery requests (creating and deleting queue
files is by far the most expensive part of Postfix queue management).
In the time since that text in MILTER_README was written, Milter
applications have been written to handle the case that {i} is not
available before the DATA command.
Wietse
