Mailbox does not exist

[Jacob Friis Larsen]

I am authenticating users via saslauthd, but when creating a new user 
via web-cyradm my E-Mail client reports that the mailbox does not exist.
According to the log, the user is authenticated.

When I send mail to the new account, Postfix says: data format error. 
Mailbox does not exist.

I have created another user via cyradm, which have no problems.
I can change all settings via web-cyradm without problems.
What could be wrong?
Jacob
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