[Dovecot] execvp /usr/local/libexec/dovecot/dovecot-lda: Permission denied

[Edward Carraro]

I'm trying to follow the instructions for configuring Dovecot LMTP with
postfix for virtual domains but whenever mail arrives, in /var/log/maillog,
I see

Sep 23 16:01:20 mybox postfix/pipe[572]: 999C83206C6: to=<
user at mytest.domain.com>, relay=dovecot, delay=0.08, delays=0.04/0.01/0/0.03,
dsn=4.3.0, status=deferred (temporary failure. Command output: pipe: fatal:
pipe_command: execvp /usr/local/libexec/dovecot/dovecot-lda: Permission
denied )

ls -lh for /usr/local/libexec/dovecot/dovecot-lda
-rwxr-xr-x 1 root staff  62K Sep 20 15:15 dovecot-lda

It will deliver mail when I do the sudo invocation of dovecot-lda, but I
thought LMTP was suppose to be an alternative to that

postfix/main.cf:
virtual_transport = dovecot
virtual_mailbox_domains = mytest.domain.com
dovecot_destination_recipient_limit = 1

/etc/postfix/master.cf:
dovecot   unix  -       n       n       -       -       pipe
  flags=DRhu user=vmail:vmail argv=/usr/local/libexec/dovecot/dovecot-lda -f
${sender} -d ${recipient}

/usr/local/etc/dovecot/conf.d/10-master.conf:
service auth {
  unix_listener auth-userdb {
    mode = 0600
    user = vmail
    #group = vmail
  }
}

service lmtp {
  unix_listener /var/spool/postfix/private/dovecot-lmtp {
   group = postfix
   mode = 0660
   user = postfix
  }

  inet_listener lmtp {
    port = 24
  }

  user = vmail
}

Did I miss something in my config?