Yesterday evening I had a couple of complaints that mail wasn't arriving for a number of hosted domains.
Further investigation showed that the server seemed to be in a perpetual state of CONTACTING BLACKLIST (shown in CommuniGator SMTP Monitor).
today I've had a look and it seems that my first DNS entry isn't resolving addresses, but the second (or alternative) does.
Would this hold up contacting the blacklists servers? surely they would eventually give up on the first DNS server and move to the second for resolution?
That depends on how 'hard' the failure for the first one is. If the query is met with a quick definitive error (i.e. a host unreachable or port unreachable ICMP packet from the nameserver or some router in the path) then the next nameserver should be tried swiftly. If (more likely) the first nameserver is getting the query but simply taking forever to answer it, then the timeout waiting for a response is likely to be on the order of 2 minutes before the second machine is queries.
The main lesson: don't point your DNS at broken nameservers.
--
Bill Cole [EMAIL PROTECTED]
############################################################# This message is sent to you because you are subscribed to the mailing list <[EMAIL PROTECTED]>. To unsubscribe, E-mail to: <[EMAIL PROTECTED]> To switch to the DIGEST mode, E-mail to <[EMAIL PROTECTED]> To switch to the INDEX mode, E-mail to <[EMAIL PROTECTED]> Send administrative queries to <[EMAIL PROTECTED]>
