I'm running Dovecot 2.2.27 (c0f36b0) on Debian Stretch and I'm having some trouble with LMTP delivery from Postfix to Dovecot. The message in the logs is Mar 9 09:21:19 mail postfix/smtpd[3295]: NOQUEUE: reject: RCPT from some.mail.server[1.2.3.4]: 450 4.1.1 <alias at my.domain>: Recipient address rejected: unverified address: host my.mail.server[private/dovecot-lmtp] said: 550 5.1.1 <user at my.domain> User doesn't exist: user at my.domain (in reply to RCPT TO command); from=<someone at another.domain> to=<alias at my.domain> proto=ESMTP helo=<some.mail.server> However, testing my installation with doveadm works fine: doveadm user -u user at my.domain userdb: user at my.domain user : user at my.domain uid : 5000 gid : 5000 home : /srv/mail/vhosts/my.domain/user doveadm auth test user at my.domain passdb: user at my.domain auth succeeded I'm using a static userdb and a ldap passdb: # /etc/dovecot/conf.d/auth-ldap.conf.ext passdb { driver = ldap args = /etc/dovecot/dovecot-ldap.conf.ext } userdb { driver = static args = uid=vmail gid=vmail home=/srv/mail/vhosts/%d/%n } And my LDAP config reads like this # /etc/dovecot/dovecot-ldap.conf.ext uris = ldap://127.0.0.1 dn = uid=dovecot,ou=services,dc=my,dc=domain dnpass = ********* auth_bind = yes auth_bind_userdn = cn=%u,ou=mail,dc=my,dc=domain ldap_version = 3 base = ou=mail,dc=querco,dc=org deref = never scope = onelevel user_attrs user_filter (&(objectclass=PostfixBookMailAccount)(mailEnabled=TRUE)(cn=%u)) pass_attrs = cn=user,userPassword=password pass_filter (&(objectclass=PostfixBookMailAccount)(mailEnabled=TRUE)(cn=%u)) iterate_attrs = cn=user iterate_filter = (&(objectclass=PostfixBookMailAccount)(mailEnabled=TRUE)) Sending the mail straight to user at my.domain works. Sending it to another alias works as well. Is there some caching problem and if so how to delete the cache (reboot didn't work)? Any pointers are highly appreciated.