Hi,
A pre-release domain would be between expiry date and redemption period. Unfortunately this is hard to tell just from a registry whois query, so you will also have to query the registrar's whois, which unfortunately does not have any standard formats. The problem is that "pre-release" is nothing registry mandated, so it's implemented at the registrar level.
On day 0 (the expiry date), the registry auto-renews a domain. So if the domain originally expired on Oct 7, 2006 the registry whois will now show Oct 7, 2007, even though the domain has not been actively renewed. The registrar is now charged for this domain auto-renewal, but the registrar can get a refund if it deleted the name (or it transfers away) within the next 45 days.
Most registrars will delete the domain between day 40 and 45 - however a pre-release domain is never deleted if there are any bids on it. It will be listed in auctions anywhere in this 40 day period. In many cases the original registrant can reclaim the domain for about 75 days, which basically is the same amount of days that the registrant would have if the domain ended up in the redemption period.
So if there were no bids on the name, the registrar would then delete the name from their system between day 40 and 45. The domain then enters the redemption grace period, which lasts for 30 days. After this period it goes into "pending delete", which lasts another five days before the domain name becomes available again (and will most likely be re-registered by someone - at the least for traffic testing).
While a name is in pre-release it originally would have been on "REGISTRAR-HOLD" and thus would be removed from the zonefiles, but nowaydays many expired domains are being tested for traffic, so this is not a reliable indicator.
Since pre-release domains are sold at special partners of the registrars (because technically the domain never drops, it's just transferred), you should be able to get lists of those names at the corresponding partners.
Some examples:
Networksolutions, Register.com and apparently now also Melbourne IT pre-release names can be seen at Snapnames, where they are listed under "Priority Partners":
http://www.snapnames.com/file_dl.sn?file=sntflist.zip
NameWinner will have the Dotster names:
http://www.namewinner.com/expiring.php
Enom will have their own
And on and on...
Of course all of this differs from registrar to registrar and TLD to TLD - most of the text refers to COM/NET.
This turned out to be quite lenghty - hope it's still understandable.
/Frank
