[Dovecot] Enable IMAP metadata

data/conf/dovecot/dovecot.conf

@@ -239,8 +239,10 @@ userdb {
   driver = sql
 }
 protocol imap {
+  imap_metadata = yes
   mail_plugins = quota imap_quota imap_acl acl zlib imap_zlib imap_sieve listescape #mail_crypt
 }
+mail_attribute_dict = file:%h/dovecot-attributes
 protocol lmtp {
   mail_plugins = quota sieve acl zlib listescape #mail_crypt
   auth_socket_path = /usr/local/var/run/dovecot/auth-master