Hi there,
We have a few different guides available that offer guidance on setting up SMTP mail servers and for configuring DNS records. You'll want to consult our Running a Mail Server guide - it has a lot of good information, including how to setup MX and SPF records:
To improve mail deliverability, you'll want to configure rDNS for any mailing Linodes you deploy. Our guides on DNS and rDNS records are linked below:
With regards to configuring DKIM and DMARC, I found some resources that you'll want to consult:
Once your DNS configuration is complete, it's worth noting that these changes can take up to 48 hours to fully propagate across the globe. You can review the status of your DNS records by using a website like DNSChecker.
It's worth noting that I'm not an expert in the intricacies of CyberPanel, and our Support team is limited in our ability to assist with custom software configurations as they fall outside the scope of Linode Support. With that said, I've done some research and located a blog post on the website TonyTeachesTech that offers a tutorial for configuring CyberPanel's SMTP server on a Linode.
If you run into issues with configuring this, you may want to consider posting a question to our Community Questions site. This website is where our community of passionate users work together to find solutions for these types of out of scope software configuration situations. You may also want to consider utilizing the services of a freelance system administrator from a website such as Upwork.com or Freelancer.com, these sites may even have someone who is local to you.
As it appears you might benefit from some precise consulting, you may want to reach out to our Professional Services team. They are here to help you understand how you can maximize Linode services to suit your specific use case. You can contact our Professional Services team at the link below:
I hope that this information helps get you pointed in the direction of a solution. Should you have any additional questions or concerns, please feel free to let us know. We're here to help in any way that we can.
Sincerely, Brendan (He/Him) Linode Support Team
