MyDNS notify not working

[MrM]

I know this has been discussed a million times, but I just can't get it working.

I'm running ISPconfig 3.0.3 (just upgraded from 3.0.1.6) on Ubuntu 9.04. On this server, I have MyDNS 1.2.8.27 as the master DNS. Then I have a second server running bind9 on Ubuntu 10.04 as the slave DNS (no ISPconfig here).

On the master (MyDNS) I have:

allow-axfr = yes
allow-tcp = yes
allow-update = yes
notify-enabled = yes
notify-source = 0.0.0.0

Also, each zone has the slave's IP in the xfer field.

On the slave (bind9) I have:

server <MASTER_IP> {
    request-ixfr no;
};

As well as all the zones from the master like this:

zone "<DOMAIN>" {
    type slave;
    file "/var/cache/bind/db.<DOMAIN>";
    masters { <MASTER_IP>; };
};

The problem is, the slave only receives notifies when MyDNS is restarted on the master. However, if I change a DNS record in ISPconfig, no notification is sent to the slave, and consequently the slave does not receive the updated record. If I run `rndc retransfer <DOMAIN>` on the slave, the record gets updated.

What could be the cause of this problem?