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Got two active directory sites with two exchange 2010 servers one in &nbsp;each site. Each server having CAS,hub and mailbox roles.<br />
&nbsp;<br />
Two send conenctors have been created one at each site to send extranl email.At the site A evry now and then emails are struck int he queue with the message &quot;451 4.4.0 primary target IP address responded with 421 4.4.2 connection dropped due to connectionreset attempted failove to alternate host but that didnot succeed&quot;.<br />
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Don't need to do any thing it does clear up it self once logged onto the server.<br />
&nbsp;<br />
It happens to all the domains.<br />
&nbsp;<br />
we are using Cisco ASA 5520 and disbled ESMTP.<br />
&nbsp;<br />
Enabled SMTP verbose logging and didn't help much.<br />
&nbsp;<br />
Send connector are using DNS and no smart hosts.<br />
&nbsp;<br />
TCP offloading has been disabled on the exchange server<br />

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Got two active directory sites with two exchange 2010 servers one in  each site. Each server having CAS,hub and mailbox roles.
 
Two send conenctors have been created one at each site to send extranl email.At the site A evry now and then emails are struck int he queue with the message "451 4.4.0 primary target IP address responded with 421 4.4.2 connection dropped due to connectionreset attempted failove to alternate host but that didnot succeed".
 
Don't need to do any thing it does clear up it self once logged onto the server.
 
It happens to all the domains.
 
we are using Cisco ASA 5520 and disbled ESMTP.
 
Enabled SMTP verbose logging and didn't help much.
 
Send connector are using DNS and no smart hosts.
 
TCP offloading has been disabled on the exchange server


451 4.4.0 primary target IP address responded with 421 4.4.2 connection dropped due to connectionreset attempted failove to alternate host but that didnot succeed

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

Hardware-based firewalls provide more sophisticated protection for inbound and outbound traffic than the simple Windows software firewall or the basic NAT firewalls found in routers. These devices implement techniques such as stateful packet inspection, deep packet inspection, and content filtering; and may include built-in antivirus and anti-malware protection.

Hardware Firewalls

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.