Configuring reverse DNS validation
You can use reverse DNS as an additional form of sender verification. A reverse DNS lookup finds the domain name based on the IP address. Because a reverse DNS lookup enables anyone to view the source of a connection, many bad senders do not have reverse DNS records, or have false reverse DNS records.
- To configure reverse DNS validation
- In the Control Center, clickProtocols > SMTP > Settings.
- On theSMTPtab, underDNS Validation, check any of the following options:
- Reject connections where no reverse DNS record exists for the connecting IP address
- Reject connections where the reverse DNS record exists for the connecting IP address, but the 'A' or 'AAAA' record of the resulting domain does not match the connecting IP address
- Reject connections where the domain provided at HELO and EHLO has neither an 'A', nor an 'AAAA', nor an 'MX' record in DNS
- Reject messages where the domain provided in the MAIL FROM address has neither an 'A', nor an 'AAAA', nor an 'MX' record in DNS
- Optionally, you can edit theReject messagetext for any option that you checked.
- ClickSave.