Dovecot with pam authentication and user at domain

[Christian Schneider]

Hello all,
I'm trying to setup dovecot for local users with pam authentication.
The passdb and userdb entries are as follows:

passdb {
  args = username_format=%n
  driver = pam
}
userdb {
  args = username_format=%n
  driver = passwd
}

Using "doveadm user chriss" returns the user record as expected, but "doveadm 
user chriss at testmail.ch-sc.de" gives an error:
field   valueuserdb lookup: user chriss at testmail.ch-sc.de doesn't exist

As far as I understand, username_format=%n should drop the domain part and 
only search for the user in the userdb, but it doesn't. What am I missing?

Greetings
Christian

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