ZIMBRA MTA (MESSAGE TRANSFER AGENT)

Zimbra Administration -> Configure -> Global Settings -> MTA Protocol Checks: reject_invalid_helo_hostname – Hostname in greeting violates RFC reject_non_fqdn_helo_hostname – Client must greet with a fully qualified hostname reject_non_fqdn_sender – Sender address must be fully qualified DNS Checks: reject_unknown_client_hostname – Client’s IP address reject_unknown_helo_hostname – Hostname in greeting reject_unknown_sender_domain – Sender’s domain Client RBLs