Running a 2008 SBS & a strange problem just started, so let me give you the history...
Was using 2 bonded T1s for phone & internet & upgraded to 10 MBs Fiber. All my IP addresses remained the same, after switchover, ran speed tests from a couple of computers & was getting 10-11 MBs up & down, all looed good. Next morning, I started getting calls that internet pages were very slow to load, timing out in some cases & emails were bouncing back. Called ISP, who reported no problems in the area, so I started digging. When looking in my Que Manager, I found 3 domains not accepting mail, one with the message '451 4.4.0 DNS Query Failed' & the other two with '451 4.4.0 Primary target IP address responded with: "421 4.2.1 Unable to connect." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts.'.
Went to try nslookup & it's coming back with;
Default Server: UnKnown
I am not using IPv6, but from what I've read, it's needed with SBS 2008 and/or Exchange 2007.
My SBS does have its own address as its only DNS server in the settings.
If I go to DNS in administrative tools, right click server & tell it launch nslookup, it lists correct name & address . I can enter set type=mx, then enter one of the problem domain names & get the correct information back.
Again, I want to add that this all started after an upgrade to a fiber line.
Where do I start?
Any advice appreciated!