For the last few days we've been having problems with the domain name mail.colourcentre.net.au.
Approximately every 5-6 hours it stops resolving to an IP address so all emails to this domain start failing and get queued instead.
I've worked out that opening AD DNS and going 'Clear Cache' on the two primary AD servers fixes the resolution problem temporarily and then the queued emails slowly start filtering through again.
This is an external domain but we've heard from them that they changed host on Friday the 27th which is now 5 days ago.
Anyone have any idea what could be happening and how to resolve this issue? I'm now assuming the DNS problems must be on our end as doing the cache clear gets it resolving again straight away. However we are not aware of any problems with other domains and can't see any errors in event logs on the AD servers.