How do I set up rDNS for sending emails while behind a NodeBalancer?
I'd like to send emails from my Linode, but my domain is configured using a NodeBalancer. On the Linode Compute Instance runs a Rails app with Traefik and the NodeBalancer works as a reverse proxy.
Say my NodeBalancer IP is 1x9.1y4.1z1.121, my back-end server IP is 1x2.1y4.2z4.79, and my domain name is mydomain.com, what are the exact steps to enable sending emails?
Notes
I looked for Linode guides about the matter but it seems there isn't one for the case when the Compute Instance is behind a NodeBalancer.
I already read these similar questions:
- How do I setup revers DNS if I am using a nodebalancer
- How do I set up rDNS for email while behind a NodeBalancer?
If I'm undestanding what to do from the above questions and guides like 1, 2, and 3, I should do something like the following for each back-end server.
In Domains:
- Set a new MX Record with Mail Server mail-1x2-1y4-2z4-79.mydomain.com
- Set a new A/AAAA Record with Hostname mail-1x2-1y4-2z4-79 and IP Address 1x2.1y4.2z4.79
And then? What to do in Linodes > my-linode-label > Network? Currently I've this.
1 Reply
jhartman
Linode Staff
As mentioned in this article you previously linked, there is no way to set a Reverse DNS/PTR record on a NodeBalancer at this time.
In general, mail servers should not be proxied since many large providers like Microsoft will automatically block mail originating from servers without proper mailing records (rDNS/PTR, MX, and SPF/TXT) or from servers that attempt to obfuscate their IP information. Although you don't appear to be doing this for nefarious reasons, they do not see it as such, so you will need to figure out an alternate solution to this issue.
One way to get around this would be to use the NodeBalancer as your frontend for all services except mailing. You would designate one backend node as your mail server and point an A Record directly at that Linode's IPv4/IPv6 address so that your could then create your mailing DNS records accordingly.
Alternatively, you could create a Linode independent of your NodeBalancer environment that is solely responsible for mailing. All other functions would be performed by your NodeBalancer + Backend Nodes setup, and all mailing tasks would be handled by that Linode as described in our SMTP/mailing guide: