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@my.domain: Recipient address rejected: unverified address: host my.mail.server[private/dovecot-lmtp] said: 550 5.1.1 user@my.domain User doesn't exist: user@my.domain (in reply to RCPT TO command); from=someone@another.domain to=alias@my.domain proto=ESMTP helo=

However, testing my installation with doveadm works fine:

doveadm user -u user@my.domain userdb: user@my.domain user : user@my.domain uid : 5000 gid : 5000 home : /srv/mail/vhosts/my.domain/user

doveadm auth test user@my.domain passdb: user@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@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.