Lets say I have the following DNS active for domain
example.com (leaving out priority and ttl)
example.com A 18.104.22.168 mx.example.com A 22.214.171.124 example.com MX mx.example.com
Now, this is a valid DNS record. If I were to add the following mx record, would that cause any problems?
mx.example.com MX mx.example.com
I have tested this, and it seems to work, but I want to be sure.
The reason is, I always used email@example.com to email without this last mx record added. But some services fail because they're not using the main domain, but rather check for the subdomain if that mx record is present. Adding the mx record seems to allwo the services to work, but I now am worried it may cause problems for actually sending/receiving email.
Also, I have set the priority for the new mx record to be lower to the original one, so in theory that should make it always choose the first one, but I'm curious it would even work if the priorities were reversed.