[Dovecot] Duplicate namespace prefix: ""

[Silvio Siefke]

Hello,

i try to run the mail system which explain dovecot in the wiki. 

http://wiki2.dovecot.org/HowTo/VirtualUserFlatFilesPostfix

I have that complete write in the config, only the domain and user
settings i changed. But something is wrong but i not found where
is the mistake.

<dovecot.log>
Feb 03 16:12:52 lmtp(1079, webmaster at silviosiefke.de): Error: user webmaster at silviosiefke.de: Initialization failed: namespace configuration error: Duplicate namespace prefix: ""

<mail.log>
Feb  3 16:16:14 ks3374456 postfix/qmgr[1067]: 311A324525D: from=<double-bounce at ks3374456.kimsufi.com>, size=254, nrcpt=1 (queue active)
Feb  3 16:16:14 ks3374456 postfix/lmtp[1308]: 311A324525D: to=<info at silviosiefke.de>, relay=ks3374456.kimsufi.com[private/dovecot-lmtp], delay=0.09, delays=0.04/0.01/0/0.04, dsn=5.1.1, status=undeliverable (host ks3374456.kimsufi.com[private/dovecot-lmtp] said: 550 5.1.1 <info at silviosiefke.de> User doesn't exist: info at silviosiefke.de (in reply to RCPT TO command))
Feb  3 16:16:14 ks3374456 postfix/qmgr[1067]: 311A324525D: removed


Has someone an idea what can be wrong.

Thank you for help & Nice Day
Silvio