<div>
Tried to disable firewall &nbsp;and then check.<br />
<br />
Make sure your AD site link configured properly. If the problem with your AD site link this might be casue the problem.<br />
<br />
Your exchange site link also configure properly.<br />
<br />
For more info refer below link:<br />
<br />
<a href="http://technet.microsoft.com/en-in/library/bb266946(v=exchg.141).aspx" rel="ugc">http://technet.microsoft.com/en-in/library/bb266946(v=exchg.141).aspx</a>
</div>


<div>
Firewall configuration change helped to solve the issue.
</div>


<div>
<div class="content wysiwyg-content">
Experts,<br />
<br />
we have 4 exchange servers (A,B,C,D) in 3 locations and all are connected with a DAG and runs communicate &nbsp;through a VPN.<br />
<br />
Exchange D was setup recently. Since then we are having public folder Folder Content queues to Exchange D from other exchanges(A,B,C) time to time. Also Exchange D is our failover email receiving server and when an email comes there it gets in to the queue as well. <br />
<br />
this is the error I'm getting.<br />
“451 5.7.3 Cannot achieve Exchange Server authentication.&quot; Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts”<br />
<br />
i have checked all the connectors and it all configured correctly.<br />
<br />
this never happened when we were having only 3 servers before.<br />
<br />
Could this be a firewall issue?<br />
<br />
Please help.<br />
<br />
Thank you.
</div>
</div>


Experts,

we have 4 exchange servers (A,B,C,D) in 3 locations and all are connected with a DAG and runs communicate  through a VPN.

Exchange D was setup recently. Since then we are having public folder Folder Content queues to Exchange D from other exchanges(A,B,C) time to time. Also Exchange D is our failover email receiving server and when an email comes there it gets in to the queue as well. 

this is the error I'm getting.
“451 5.7.3 Cannot achieve Exchange Server authentication." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts”

i have checked all the connectors and it all configured correctly.

this never happened when we were having only 3 servers before.

Could this be a firewall issue?

Please help.

Thank you.

Tried to disable firewall  and then check.

Make sure your AD site link configured properly. If the problem with your AD site link this might be casue the problem.

Your exchange site link also configure properly.

For more info refer below link:

http://technet.microsoft.com/en-in/library/bb266946(v=exchg.141).aspx

Firewall configuration change helped to solve the issue.

SMTP relay to remote AD site -

Experts,

we have 4 exchange servers (A,B,C,D) in 3 locations and all are connected with a DAG and runs communicate  through a VPN.

Exchange D was setup recently. Since then we are having public folder Folder Content queues to Exchange D from other exchanges(A,B,C) time to time. Also Exchange D is our failover email receiving server and when an email comes there it gets in to the queue as well. 

this is the error I&#39;m getting.
“451 5.7.3 Cannot achieve Exchange Server authentication.&quot; Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts”

i have checked all the connectors and it all configured correctly.

this never happened when we were having only 3 servers before.

Could this be a firewall issue?

Please help.

Thank you.

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.

Exchange

Active Directory (AD) is a Microsoft brand for identity-related capabilities. In the on-premises world, Windows Server AD provides a set of identity capabilities and services, and is hugely popular (88% of Fortune 1000 and 95% of enterprises use AD). This topic includes all things Active Directory including DNS, Group Policy, DFS, troubleshooting, ADFS, and all other topics under the Microsoft AD and identity umbrella.

Active Directory

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.