I have Ubuntu 11.04, Postfix, Dovecot installed.
I've noticed when I send mail from user1 (existing virtual user) to non existing user2 (non existing virtual user), mail is "delivered", folder user2 is created in
home vmail mycompany
with Maildir in it.

Sending user doesn't get any message that user is unknown.

In mail.log I have found these lines:
postfix/pickup[2214]: 3A38745BCF: uid=33 from=<user1>
postfix/cleanup[6427]: 3A38745BCF: message-id=<193bdeefafab0d49467989c38614869.squirrel[at]192.1 68.100.30>
postfix/qmgr[2215]: 3A38745BCF: from=<user1>, size=676, nrcpt=1 (queue active)
postfix/pipe[6431]: 3A38745BCF: to=<user2>, relay=dovecot, delay=0.04, delays=0.02/0/0/0.02, dsn=2.0.0, status=sent (delivered via dovecot service)
postfix/qmgr[2215]: 3A38745BCF: removed

When I send mail from my gmail account to non existing user2, I get:
SMTP error: 550 5.1.1 <user2>: Recipient address rejected: User unknown in virtual mailbox table

How can I resolve this? When I send from user1 to non existing user2 I should get similar message.

Thanks in advance.