When a DNS transfer is made to a new host what is 'normal' practice among operators in regards to the old record?

Do you delete it immmediately, wait a specified time and then delete it, or wait to hear from the customer?

Speaking personally only, my view on this one is: - DNS should honour the Registry. Thus if Nameservers are redelegated - I have to assume the client themselves has done this, as they _should_ be the only ones with access - I will query the new authoritives and retain any services mapped towards me (web A or MX's) and purge the zones from my DNS. I then advise client that I have done so and will await further advice. I always have the option of reloading the zone (which I have retained) should it need to be 'undone' but given that the domain owner is the only person who can move the domain's authoritive NS in registry, i'm essentially providing them a service by quickly removing legacy zones. I know of ISPs who will purge everything by default within 24-48 hours of a zone transfer; As long as requests to do this sooner (from the customer) are honoured this seems like a fair-enough proposition. (Amazing sometimes that domain owners give their third-party-tech-support-contractor... sometimes its good to hedge incase the client decides this isn't what theyre after at all...) All comments IMHO, of course. Mark.