Once you set up a VPS on Linode you will also need to set up email by installing a Message Transfer Agent such as Sendmail or Postfix. If you do not set up Reverse DNS however, your webserver will not be able to send out email, and if you send out an email to a gmail address gmail will send your server a message like this:
050 550-5.7.1 [2600:3c03::f03c:91ff:feb0:dac3] Our system has detected that this
050 550-5.7.1 message does not meet IPv6 sending guidelines regarding PTR r ecords
050 550-5.7.1 and authentication. Please review
050 550-5.7.1 https://support.google.com/mail/?p=ipv6_authentication_error for more
050 550 5.7.1 information. b87si2979083qkb.118 – gsmtp
Checking https://support.google.com/mail/answer/81126?p=ipv6_authentication_error&rd=1#authentication will bring you this page, which explains the error as your server not having a ‘reverse dns’, or the association of a domain name with an IP address.
To fix this on Linode, login to Manager.linode.com, and click the ‘Remote Access’ tab.
- On Public IPs, click ‘Reverse DNS’
- Enter a hostname, and once you click Look Up this page will appear, such as on mine where I want to associate my IP addresses (both ipv4 and ipv6) to the hostname ‘majortom.kaijuhost.com’.
- Click ‘YES’ to either. If you wish to add the other as well, repeat the process. Wait 24 hours for the DNS to fully spread around the ‘net.
More information here.