On Mon, 17 Jan 2005 10:39:36 -0500, Rich Greenberg <[log in to unmask]> wrote:

>Throughout this event, lists that I subscribe to which are
>hosted on Apple (not sure about Peach) continued to be delivered
>properly.  

Apple and Peach use the same DNS server.  It seems unlikely they would give
different results.

>Does Lsoft not use the usual DNS systems 

We use regular DNS.

>that expire records after (usually) 24 hours,  

The time-to-live (TTL) for how long a (local) nameserver should cache a DNS
record is set by the Start-of-authority record of the domain in question.  The
new/current record for Panix.com sets that at 900 seconds (15 minutes).  A
more typical time is 86400 seconds (24 hrs).  

>or does it internally cache certain domains
>on a longer term basis?

Actually the TTL is expressed as 2 values, a 'minimum' time (the common TTL
referred to above) which represents how long the information can be considered
'authoritative' or valid, and an 'expiration' time after which the record must
be considered invalid and discarded.  If a DNS refresh lookup is attempted
after the minimum time has expired, but before the maximum expiration time has
expired, AND the lookup attempt fails to return new information, the DNS
server will return the information to the requesting mail server from cache as
'non-authoritative'.  It is then up to the mail server to decide whether or
not to take a chance using this information.  Usually, mail servers will try
it.  And if it works (as it apparently did in your case) then you get the
mail.

I don't know that this is exactly what happened in this case, but it sounds
likely.