cyrus imapd, lmtp, postfix and case sensitivity bouncing emails

[Carl Brewer]

G'day,
I have a NetBSD (pkgsrc) box that I'm moving email from an old sendmail 
setup over to, using cyrus imapd and the new box is using postfix (from 
pkgsrc, v2.11.3).

A weird problem, it's bouncing emails if the domain name is uppercase. 
I have set
lmtp_downcase_rcpt: 1
but it doesn't seem to have helped.

my imapd.conf file is :


configdirectory: /var/imap
partition-default: /var/spool/imap
sieveusehomedir: true
hashimapspool: false
sendmail: /usr/sbin/sendmail
sasl_mech_list: PLAIN
altnamespace: yes
unixhierarchysep: yes
virtdomains: userid
defaultdomain: bl.echidna.id.au
allowplaintext: yes
admins: cyrus
sasl_pwcheck_method: auxprop
tls_cert_file: /var/imap/server.pem
tls_key_file: /var/imap/server.pem
lmtp_downcase_rcpt: 1


and postfix's main.cf :

mailbox_transport = lmtp:unix:/var/imap/socket/lmtp
virtual_transport = lmtp:unix:/var/imap/socket/lmtp

Relevant versions of everything :

cyrus-sasl-2.1.26nb3 Simple Authentication and Security Layer
cyrus-imapd-2.4.17nb6 Cyrus IMAP server
cyrus-saslauthd-2.1.26nb2 Cyrus SASL plaintext authentication daemon
postfix-2.11.3      Postfix SMTP server and tools


here's an example log :

Feb 13 08:26:44  postfix/smtpd[4578]: NOQUEUE: reject: RCPT from 
unknown[175.107.182.124]: 450 4.1.1 <carl at ABOC.COM.AU>: Recipient 
address rejected: unverified address: host 
rollcage3.bl.echidna.id.au[/var/imap/socket/lmtp] said: 550-Mailbox 
unknown.  Either there is no mailbox associated with this 550-name or 
you do not have authorization to see it. 550 5.1.1 User unknown (in 
reply to RCPT TO command); from=<carl at svr4.aboc.net.au> 
to=<carl at ABOC.COM.AU> proto=ESMTP helo=<svr4.aboc.net.au>

It's fine with lowercase domain names though ...

Feb 13 08:36:33  postfix/lmtp[8436]: CBA4A1B3D4A3: 
to=<CaRl at aboc.com.au>, 
relay=rollcage3.bl.echidna.id.au[/var/imap/socket/lmtp], delay=0, 
delays=0/0/0/0, dsn=2.1.5, status=deliverable (250 2.1.5 ok)


Any ideas?

Thank you

Carl