Hello. I hope these aren't silly questions: How does Postfix (2.9.6) determine whether the local mail system is backup or primary MX when permit_mx_backup is specified in main.cf? Is it just MX record priorities in DNS?
http://www.postfix.org/postconf.5.html#permit_mx_backup * permit_mx_backup Permit the request when the local mail system is backup MX for the RCPT TO domain, ... <snip> *Safety: as of Postfix version 2.3, permit_mx_backup no longer accepts the address when the local mail system is primary MX for the recipient domain. Does this mean a MX record pointing to a mail host w/ permit_mx_backup all that's needed to relay to it?
