troubleshooting Question

Exchange 2010 DNS error

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ITMND asked on
Microsoft Server OSExchangeSBS
21 Comments2 Solutions618 ViewsLast Modified:
I just installed an SBS 2011 server and incoming mail works fine, but outgoing outside of local addresses won't go.  I've tried various DNS settings, telling it to use external DNS, disabling IPv6, nothing seems to work.  My firewall says it's passing port 25 traffic outbound and AT&T verified they are no longer blocking port 25.  I've tried using a smarthost and without a smarthost.  The message I'm getting is:

451 4.4.0 primary target IP address responded with "421.4.4.2 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
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David Atkin
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