[tankenmate]

I suspect those A records are probably grandfathered and they are of course ccTLDs so the rules are different. None of the gTLDs have A records for their TLD (although they almost certainly have glue A records). From memory I queried John Craine (ICANN Security, Stability and Resiliency Director) about this a number of years ago and again if I remember accurately his response was that they wouldn't allow any additional types of records. I suspect this is a policy decision rather than a technical one.

RFC 2822 has been superceded by RFC 5322. The problem is not being allowed to put MX records in the zone for a TLD, and hence the mail is not routeable. Also remember that you would need to differentiate between "me@mytld<.localdomain>" and "me@mytld.", I'm not sure if all MTA software (let alone MUA) will do the right thing with differentiation. This is probably considered to impact stability and hence is discouraged.