When to use proxymap for accessing maps
From http://archives.neohapsis.com/archives/postfix/2010-02/0047.html
Use "proxy:ldap:${config_directory}/ldap-aliases.cf", LDAP servers typically don't like the connection concurrency that results from each smtpd(8) and cleanup(8) using a separate connection.
Don't do this, however, with tables that are used by trivial-rewrite, specifically at least:
- relay_domains
- mydestination
- virtual_mailbox_domains
- virtual_alias_domains
- transport_maps
- relocated_maps