[Dovecot] %d is empty in mail_location

[Phil Howard]

I have this in dovecot-postfix.conf:

mail_location =
maildir:/home/mail/dnamesum=%12MLd/dname=%Ld/unamesum=%12MLn/uname=%Ln/mail

Yes, it is excessive, but that's just for testing.  The pattern I really
want is less clear for debugging.  In postfix/main.cf I have:

mailbox_command = /usr/lib/dovecot/deliver -c
/etc/dovecot/dovecot-postfix.conf -a "${RECIPIENT}"

I verified through strace that -a "${RECIPIENT}" is in fact getting a full
user at domain address.  The problem is that %d and %Ld are coming up as empty,
and %12MLd is giving me the first 12 hex characters of an md5 of an empty
content.  It's losing the domain name somewhere.  It's in the mail headers
and in the -a option.  So what else is needed?