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=))))) Yes, I'm idiot! This is so obvious and I forgot to open port 25! Thanks a lot busbar!
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=))))) Yes, I'm idiot! This is so obvious and I forgot to open port 25! Thanks a lot busbar!

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I have two Exchange servers. One of them has CAS, HUB, MB roles. Another one has HUB, MB roles. These servers are in DAG. <br />
<br />
Before current config there there was only one HUB server and messages were sending normally. <br />
<br />
After I installed HUB server on second server messages can be send only through old HUB server and when they are sending through new one they hangs in queue with error:<br />
<br />
Delivery Type DnsConnectorDelivery<br />
<br />
451 4.4.0 Primary target IP address responded with: &quot;421 4.2.1 Unable to connect.&quot; Attempted failover to alternate host, but that did not suceed. Either there are no alternate hosts, or delivery failed to all alternate hosts.<br />
<br />
Incoming messages passes normally. <br />
<br />
Send connectors are similar for both HUB servers.<br />
<br />
What can cause such a problem?
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I have two Exchange servers. One of them has CAS, HUB, MB roles. Another one has HUB, MB roles. These servers are in DAG. 

Before current config there there was only one HUB server and messages were sending normally. 

After I installed HUB server on second server messages can be send only through old HUB server and when they are sending through new one they hangs in queue with error:

Delivery Type DnsConnectorDelivery

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 suceed. Either there are no alternate hosts, or delivery failed to all alternate hosts.

Incoming messages passes normally. 

Send connectors are similar for both HUB servers.

What can cause such a problem?

HUB transport role in DAG

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.