Cloudflare is the registrar for my domain. Let’s call my domain “toto.com”. I have a CNAME record called “test” that points to an A record of a partner (let’s call it titi.com). So, test.toto.com directs to my partner’s server, and everything is fine. However, I have an issue with the MX records. For my main domain “toto.com,” the MX record is set to “antispam.fr,” and it works without any problems. However, I also want to add my MX record for “test” as “antispam.fr.” Some DNS servers can find it, but not all of them. When I use the dig command with Google’s DNS server, the MX resolution works fine. But when I use OVH’s DNS servers, it doesn’t work. I want to mention that this configuration has been functional for at least two years, and I’ve been experiencing issues for the past month or a few weeks.
You’ll need to disclose the real domains for anyone to help by checking.
Odd DNS behaviour like this can be caused by DNSSEC configuration issues, but without a domain we can’t know.
If test.toto.com is a CNAME, then it’s not valid to add an MX record (or any other records) for it. A CNAME means that the target should be looked up for all records, and thus any MX record for the target domain is supposed to be used. Adding additional records next to a CNAME will, at best, result in undefined and unpredictable behavior.
Hello, @i40west I didn’t believe it, but you were absolutely right. I changed my CNAME to A, and the DNS servers almost instantly detected my MX. Thank you for the information; we learn something new every day! We can close the post.