VisNetic MailServer 8.3.5 or higher has the option to deliver to a relay host when MX delivery fails. For example, when VMS receives a 5.xx, 4.xx error, timeout or connection refusal during the MX delivery process it will deliver to the host specified in the "User Relay server" option. Note that it will only deliver to the relay server if MX delivery fails. If DNS lookup fails, such as "Domain not found", it will stay in the retry queue.
1. Open the VMS admin select Mail Service - SMTP Service - Delivery tab and enable "Deliver messages via relay server when direct delivery fails".
2. Enter a relay host in the "Use relay server" field in the General tab, leave the radio button option on "Use DNS Lookup".