[Dovecot] Deliver all addresses to the same mdbox:?

[Ralf Hildebrandt]

For archiving purposes I'm delivering all addresses to the same mdbox:
like this:

passdb {
  driver = passwd-file
  args = username_format=%u /etc/dovecot/passwd
}

userdb {
  driver = static
  args = uid=1000 gid=1000 home=/home/copymail allow_all_users=yes
}

Yet I'm getting this:

Jan  3 19:03:27 mail postfix/lmtp[29378]: 3THjg02wfWzFvmL: to=<firstname.lastname at charite.de@backup.invalid>,
relay=mail.charite.de[private/dovecot-lmtp], conn_use=20, delay=323, delays=323/0/0/0, dsn=4.1.1, status=SOFTBOUNCE (host
mail.charite.de[private/dovecot-lmtp] said: 550 5.1.1 <"firstname.lastname at charite.de"@backup.invalid> User doesn't exist: "firstname.lastname at charite.de"@backup.invalid (in reply to RCPT TO
command))
(using soft_bounce = yes here in Postfix)

In short: backup.invalid is delivered to dovecot by means of LMTP
(local socket). I thought my static mapping in userdb would enable the
lmtp listener to accept ALL recipients and map their $home to
/home/copymail - why is that not working?

-- 
Ralf Hildebrandt
  Geschäftsbereich IT | Abteilung Netzwerk
  Charité - Universitätsmedizin Berlin
  Campus Benjamin Franklin
  Hindenburgdamm 30 | D-12203 Berlin
  Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962
  ralf.hildebrandt at charite.de | http://www.charite.de