I have a client that has a .TEL domain name. I recommened they not use this as their primary domain for email but as they say 'the client is always right'!!.
So, I have access to the registrant page for the domain. I tried to create the MX record there - it let me but after 5 days is doesnt appear in DNS. So I logged a call with the Registrant's support team. They gave me the URL to 'Manage my .tel domain.
In there I have a control panel where I can set the MX Record but it will only me to use a HOSTNAME and not IP address.