cant receive email, issue with [email protected]

I cant receive emails... its too extrange...
I created a domain with no problems, and upload his webpage: http://www.domain.com ... its works.

But receiving emails... if I send to [email protected] appears errors:

<[email protected]>: Host or domain name not found. Name service error
for name=www.ksXXXX.kimsufi.com type=AAAA: Host not found

ksXXXX.kimsufi.com its my server, dont have www.

But... if I send to [email protected] works
Where is the problem

Thanks.