How-To use Virtual Domains?

[EppO]

I made several updates in my configuration to be able to manage virtual
domains with cyrus and postfix but it doesn't work as it should.
I suer Postfix 2.0.18 and cyrus-imapd 2.1.16

I added to imapd.conf:
virtdomains: yes
defaultdomain: mydomain.net
unixhierarchysep: yes

And to main.cf:
mydestination = mydomain.net
mailbox_transport = lmtp:unix:/var/lib/imap/socket/lmtp

I created mailboxes using cyradmn:
cm user/toto at mydomain.net
When I do lm i see: user/toto at mydomain.net (\HasNoChildren)
I made a password to this user: saslpasswd2 -u mydomain.net toto

When I connect with an imap client, it works well, i can list my folders.
But when I try to mail this user postfix says:
<toto at mydomain.net>: host
/var/run/cyrus/socket/lmtp[/var/run/cyrus/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)

I know the trick using postfix virtual table to map cyrus user, but it's not
very clean and I would like something centralized.
Must I wait for cyrus 2.2 or is there a chance without ?

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