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