Domain without an A records

[Bind Users]

Hi

Sorry for the most stupid question that I asked.

Can it works for a domain without an A records (the sample is as below).
it just for the SMTP services only. How about the lookup result?

Thanks.

$ORIGIN .
$TTL 43200      ; 12 hours
domain.com      IN SOA  ns1.xxxxx.com. root.ns1.xxxxx.com. (
                                2001092701 ; serial
                                3600       ; refresh (1 hour)
                                300        ; retry (5 minutes)
                                604800     ; expire (1 week)
                                43200      ; minimum (12 hours)
                                )
                        NS      ns1.xxxxx.com.
                        NS      ns2.xxxxx.com.
                        MX      10 smtp.xxxxx.com.