No, MX records must not point to an IP address. MX records should point to address records (A or AAAA), domains, or hostnames.
No, MX records must not point to CNAME records. In the following example, the specified MX record for greatmail.com is invalid because it points to a CNAME : greatmail.com.com MX mail.greatmail.com mail.greatmail.com CNAME mail2.greatmail.com An MX record must point to an address record (A or AAAA). The following MX and A records are correct: greatmail.com.com MX mail.greatmail.com mail.greatmail.com. IN A 184.108.40.206