Problem about Virtual Domain

[Kai]

Hi list.
 I am using Postifx+Cyrus-imap-2.2.
Now my postfix can receive virtual domain's mail and deliver to cyrus. but
even I created the mailbox in cyradm,I still got the following message:

user1 at virtual.domain : data format error. Command output: user1: Mailbox
does not exist.

I checked my imapd's log and found only the left-hand-side of email was
delivered by Cyrus.
the log......

Aug 20 05:30:09 www master[13358]: about to exec /usr/cyrus/bin/lmtpd
Aug 20 05:30:09 www lmtpunix[13358]: executed
Aug 20 05:30:09 www lmtpunix[13358]: accepted connection
Aug 20 05:30:09 www lmtpunix[13358]: lmtp connection preauth'd as postman
Aug 20 05:30:09 www lmtpunix[13358]: append_check() of 'user.user1' failed

would someone help me ? thanks very much.
---
Kai


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