You may receive the following bounce back email message when attemping to send an email to an address hosted at Studiocoast:
This server requires PTR for unauthenticated connections
This error message can indicate the sending mail server is missing a required PTR (Reverse DNS) record.
Contact your email provider to have a PTR record enabled on your mail servers.
A Reverse DNS record is a hostname that can be discoverd by looking up the IP address.
For example looking up 18.104.22.168 (one of our mail servers) will return the hostname: trio.studiocoast.com.au
If a mail server does not have this record setup, or it is not configured correctly, email providers (including Studiocoast, and ISPs such as iiNet) will reject the email.
Thus it is important that the email provider setup a PTR to ensure emails can be delivered effectively.