MX problem

Hi
I am running a small ISP and decided to move our qmail program from our
"server" machine to a pop toaster on our "chunky-moma" machine.

The "server" is also our ns1 running 8.2.3 and the "chunky-moma" is ns2
running 9.1.

I have several unused domains and set one of these up to test the system
before I changed over - everything worked perfectly so with a modicom of
confidence I changed the MX records and "mail" CNAME for tac.com.au  to
point at the new mail server.

All worked ok except mail from remote domains was not being delivered to
the new server - in fact it was still being delivered to the old "server"
machine.

I have tried every possible configuration I can think of in the SOA
records but I must have something wrong as nothing happens when I switch
over.

It cant be firewall problem etc as the other 2 domains I have on the
system work fine - I can also telnet into port 25 and send messages to any
one on the new server on the tac.com.au domain.

I have also tried the server as MX 10 and the chunky as MX 100 then
blocked port 25 on the server but no joy.

I thought the new server maybe bogging down with the traffic so I made
every customers mail forward to 2 other domains on the new server which
would result in twice the normal traffic and this worked fine.

because the other 2 trial domains work fine that eliminates "-"
 in server names and incompatabilities between DNS versions and just about
everything else I can think of.

below are the appropriate SOA records I hope there is some obvious flaw
here as I am out of options and any help would be gratfully appreciated

"server"   ns1  primary   bind 8.2.3    RH 2.2.12

$TTL 1D
@               IN      SOA     server.tac.com.au.   support.tac.com.au. (
                        2001120302 ; serial
                        10800 ; refresh
                        3600 ; retry
                        604800 ; expire
                        86400 ; default_ttl
                        )
                IN      NS      ns1.tac.com.au.
                IN      NS      ns2.tac.com.au.
                IN      A       202.9.244.6
                IN      MX      10      server.tac.com.au.    ;change
                IN      MX      100     chunky-moma.tac.com.au.
localhost       IN      A       127.0.0.1
chunky-moma     IN      A       202.9.244.3
ns2             IN      A       202.9.244.3
server          IN      A       202.9.244.6
ns1             IN      A       202.9.244.6
core-gos        IN      A       202.9.244.7
mail            IN      CNAME   server.tac.com.au.      ;change
www             IN      CNAME   server.tac.com.au.
webmail         IN      CNAME   chunky-moma.tac.com.au.
ftp             IN      CNAME   server.tac.com.au.
telnet          IN      CNAME   server.tac.com.au.

The lines marked ";change"  are changed from server.tac.com.au to
chunky-moma.tac.com.au  - the ";change" is not in the actual file I have
added it in this email

"chunky-moma" SOA   ns2  secondary   bind 9.1   RH 2.4.20-8

$TTL 1D
@                       IN SOA  server.tac.com.au. support.tac.com.au. (
                                2001120302 ; serial
                                10800      ; refresh (3 hours)
                                3600       ; retry (1 hour)
                                604800     ; expire (1 week)
                                0          ; minimum (0 seconds)
                                )
                        NS      ns1.tac.com.au.
                        NS      ns2.tac.com.au.
                        A       202.9.244.6
                        MX      10 server.tac.com.au.      ;change
                        MX      100 chunky-moma.tac.com.au.
chunky-moma             A       202.9.244.3
ns2                     A       202.9.244.3
server                  A       202.9.244.6
ns1                     A       202.9.244.6
core-gos                A       202.9.244.7
telnet                  CNAME   server.tac.com.au.
ftp                     CNAME   server.tac.com.au.
mail                    CNAME   server.tac.com.au.         ;change
webmail                 CNAME   chunky-moma.tac.com.au.
www                     CNAME   server.tac.com.au.

this is the primary SOA for aoz.net one of the trial domains that works OK

$TTL 1D
@               IN      SOA     server.tac.com.au. support.tac.com.au. (
                        2003020501 ; serial
                        10800 ; refresh
                        3600 ; retry
                        604800 ; expire
                        86400 ; default_ttl
                        )
        IN      NS      ns1.tac.com.au.
        IN      NS      ns2.tac.com.au.
        IN      A       202.9.244.6
        IN      MX      10      chunky-moma.tac.com.au.
www     IN      CNAME   aoz.net.






-------------------------------------------------------------------------------
    TAC Systems         Phone 02 43678900  Fax 02 43672450
                        5/188 The Entrance Rd. ERINA 2250
                        Accounts accounts@xxxxxxxxxx 
                        Support  support@xxxxxxxxxx