lmtp through tcp doesn't find the mailbox

[Marten Lehmann]

Hello,

I tried to create mailboxes with cyradm (user.test at test.de and 
test at test.de). But when I'm doing a lmtp-session to deliver a message to 
test at test.de and come to the rcpt-to point, I always get:

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

What is lmtp doing at this point to check if a mailbox exists? I'm 
running completely out of ideas what to try next to get it working.

This is my imapd.conf:

configdirectory: /var/lib/imap
partition-default: /var/spool/imap
admins: cyrus cyrusd
sievedir: /var/lib/imap/sieve
sendmail: /usr/sbin/sendmail

altnamespace: true
hashimapspool: true
unixhierarchysep: true
virtdomains: userid
defaultdomain: test.de

My shortened cyrus.conf:

SERVICES {
   imap          cmd="imapd" listen="imap" prefork=5
   lmtp          cmd="lmtpd -a" listen="x.x.x.x:lmtp" prefork=0
}

Regards
Marten