named-checkzone falsely identifying my out-of-zone MX records as CNAME. Why?

Question

So, my server's primary hostname is internet.practiceofcode.com. This is defined as an A record, and the reverse lookup has been correctly configured:

 # host -t a internet.practiceofcode.com
 internet.practiceofcode.com has address 118.127.56.29

I have assigned this hostname as the MX value for a number of other domains:

 # host -t mx radic.com.au
 radic.com.au mail is handled by 10 internet.practiceofcode.com.

The zone file for that domain is as follows:

 $ORIGIN radic.com.au.
 $TTL 3600  ; 1 hour
 radic.com.au.  IN SOA  internet.practiceofcode.com. hostmaster.practiceofcode.com. (
                2011101002
                3600       ; refresh
                3600       ; retry
                604800     ; expire
                3600       ; minimum
                )
                NS  internet.practiceofcode.com.
                NS  backup.practiceofcode.com.
                MX  10 internet.practiceofcode.com.
                MX  50 backup.practiceofcode.com.
                TXT "v=spf1 a mx ?all"

However, when using named-checkzone to validate it, it (seemingly erroneously) tells me that internet.practiceofcode.com. is a CNAME:

 # named-checkzone radic.com.au. radic.com.au.zone
 zone radic.com.au/IN: radic.com.au/MX 'internet.practiceofcode.com' (out of zone) is a CNAME 'internet.practiceofcode.com.' (illegal)
 zone radic.com.au/IN: loaded serial 2011101002

I'm running Debian Squeeze:

 # cat /etc/debian_version 
 6.0.2

And Bind 9.7.3:

 # named-checkzone -v
 9.7.3

Zone file for practiceofcode.com.:

 $ORIGIN practiceofcode.com.
 $TTL 3600  ; 1 hour
 practiceofcode.com.    IN SOA  internet.practiceofcode.com. hostmaster.practiceofcode.com. (
                2011101002
                3600       ; refresh
                3600       ; retry
                604800     ; expire
                3600       ; minimum
                )
                NS  internet.practiceofcode.com.
                NS  backup.practiceofcode.com.
                MX  10 internet.practiceofcode.com.
                MX  50 backup.practiceofcode.com.
                A   72.32.231.8
                TXT "v=spf1 a mx -all"
 www                CNAME   practiceofcode.com.
 internet           A   118.127.56.29

Answer 1

There is missing a dot at the end of 'internet.practiceofcode.com' in the named-checkzone. Maybe there is a dot missing in your 'practiceofcode.com' zone ? Other idea : I put the '$ORIGIN domain' after the SOA definition, and I put a '$ORIGIN .' before SOA. Maybe it change something...