How do I set up and verify Reverse DNS Lookup?
To ensure remote mail servers reliably accept SMTP connections from the Sendio ESP, first determine the public IP address associated with it and then ensure a corresponding PTR record is set up for this address. To determine the public IP address, access the Console (SSH) Interface > Network Diagnostics > SMTP Diagnostics Test. This server will respond […]
Is reverse DNS (rDNS) important?
Yes. Many mail servers will not properly accept or process email coming from IP addresses that fail a reverse DNS lookup. Please review this FAQ for instructions on setting up a reverse DNS entry – How do I set up and verify Reverse DNS Lookup?
Why are SAV Requests and other outbound e-mail being deferred or rejected?
Many mail servers perform a Reverse DNS lookup on the originating IP address of an incoming SMTP connection. If the result of such lookup fails or the result does not translate back to a proper hostname (one associated with your domain), the SMTP connection will either be rejected, the mail will be deferred, or it […]