Hi all, i need to configure a secondary mx using posfix.. to do this i've followed this how to. When i stop postfix on the primary mx, seems that the email are received by backup mx but when i restart postfix on the primary emails are not delivered to it.. and the users cannot receive nothing. Some logs on backup mx: Code: Feb 11 22:17:19 neptune postfix/qmgr: 6D41C1200149: from=<firstname.lastname@example.org>, size=14816, nrcpt=1 (queue active) Feb 11 22:17:49 neptune postfix/smtp: 6D41C1200149: to=<email@example.com>, relay=none, delay=102080, delays=102050/0.03/30/0, dsn=4.4.1, status=deferred (connect to primarymx.domain.com[primary_MX_IP]: Connection timed out) Backup MX main.cf: Code: myhostname = neptune.domain.com mydomain = domain.com smtpd_recipient_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination, permit_mx_backup relay_domains = $mydestination domain.com testdomain.com relay_recipient_maps = maximal_queue_lifetime = 60d transport_maps = hash:/etc/postfix/transport /etc/postfix/transport : Code: domain.com smtp:primarymx.domain.com testdomain smtp:primarymx.testdomain.com Obviusly on primary mx maillog i've no logs about the emails received by backup mx.. What's my mistake? How can i solve ? Thank you so much for help!