email routing to seemingly un-routeable domains

[Jim Pazarena]

/dev/rob0 wrote:

>On Monday 2005-September-05 15:02, Jim Pazarena wrote:
>  
>
>>I have an issue cropping up with a domain name of:
>>
>>   sk.sympatico.ca
>>
>>a user claims that it is a valid domain name for a friend of his, but
>>my mail server claims it to be un-routeable,
>>    
>>
>
>How so? What does it say?
>
>  
>
>>and indeed a "dig" doesn't produce much info.
>>    
>>
>
>It has SOA, and 2 NS records. No A nor MX.
>
>  
>
>>what happens with names such as these on mail servers which actually
>>_can_ route to it? how do they do it?
>>    
>>
>
>Perhaps it is a case of differing views for their clients. I'm unsure 
>what you are asking here. Do not confuse routing with resolution.
>  
>
the question then, is,

SHOULD a mail transport agent accept an email addressed to this domain? 
with no "A" or "MX"
how would it determine how to route it ?