Hello, I'm trying to setup my server (mx2.domain.tld) as secondary mail server. It should relay all emails from known domains to proper servers - in most cases mx1.domain.tld - server in LAN, but without ISPConfig installation). On mx2.domain.tld I listed all known domains in postfix main.cf file: Code: relay_domains = domain1, domain2, domain3, ... , domain20 relay_recipient_maps = mydestination = server2.domain.tld, localhost.domain.tld, localhost relayhost = smtpd_delay_reject = no smtpd_helo_required = yes smtpd_helo_restrictions = reject_invalid_hostname, reject_unknown_hostname, reject_non_fqdn_hostname smtpd_client_restrictions = reject_unknown_client smtpd_sender_restrictions = reject_unknown_sender_domain, reject_unverified_sender Unfortunately I'm still getting such error message: I also tried to use ISPConfig feature: Emails -> Global filters -> Relay recipients but it didn't work.
Take a look here on how to setup a backup MX server without ispconfig: https://www.howtoforge.com/postfix_backup_mx
