- Markus Stumpf <[EMAIL PROTECTED]>:
| On Thu, Mar 18, 1999 at 04:35:49PM +0100, Harald Hanche-Olsen wrote:
| > - "Chris Garrigues" <[EMAIL PROTECTED]>:
| >
| > | Is it possible that these were domains in which they had just added
| > | the MX and the old zone data was still cached in various places in
| > | the DNS, so your qmail didn't have access to the latest zone yet?
| >
| > But then his server would not even be aware that it was an MX for the
| > domain in question, so the problem simply would not arise.
|
| If the sending mailer sends mail to the best-MX frequently it might
| have the MX records cached in his DNS server.
| Then the best-MX ist down and it tries the backup-MX. The mailserver
| there does a DNS query which does not succeed and *poof* ??
If it gets a temporary error, the mail remains in the queue. If it
doesn't find itself among the MXes, it will happily forward to
whatever MX it can find. It should never get an answer saying that it
is itself a best MX, if the authoritative data has never been in that
state. As far as I am aware, a caching name server must either cache
all, or none, of the pertinent data for a given name at a given time.
Otherwise, a partially filled cache might indeed lead a host to think
it is a best MX when in fact it has never been so.
- Harald
