When i try to add a record (MX) he gives me this error
What can i do?
Can you screenshot the entire screen please?
Ok, can you take another with the MX record your are trying to add (immediately before this error)?
Dun think will work on free subdomain. You need custom domain
Ok 
It should work on subdomains.
Please try entering the MX record without the period at the end. And double check that there are no space characters before, after or in between the MX record.
Ok, I’ll try so I’ll let you know