Archiving Task fails with Events 3460 & 2256 when starting a task that targets Exchange 2013 or 2016 due to RPC issues

Archiving Task fails with Events 3460 & 2256 when starting a task that targets Exchange 2013 or 2016 due to RPC issues

Article: 100034045
Last Published: 2020-03-19
Ratings: 5 2
Product(s): Enterprise Vault


When starting an Archiving Task that targets Exchange 2013 or 2016, error events 3460 and 2256 occur, and the task fails. 

Error Message

Event ID: 3460 The Task 'Exchange Mailbox Archiving Task for ExchangeServerName' failed to log on to Exchange server ' ExchangeServerName' using mailbox ''. Check that the mailbox has not been hidden, that the server is running and that the vault service account has sufficient permissions on the server.

Event ID: 2256 The Archiving Task 'Exchange Mailbox Archiving Task for EXC2' could not be started due to startup errors.




This can be due to an inability for RPC over HTTP requests from the Outlook client on the EV server to reach the Exchange server.  Some potential causes include:
1.  RPC over HTTP Proxy feature is not installed on Exchange
2.  Exchange is not listening on port 6001, the default port for RPC requests
3.  A load balancer between Enterprise Vault (EV) and Exchange is not allowing RPC traffic through
4.  A load balancer between EV and Exchange is not allowing traffic through port 6001
5.  The MapiHttpDisabled registry setting is not properly set on the EV server, thus not forcing RPC/HTTP protocol to be used.


First, consult the following article to confirm that Exchange Connection points are properly set:  100011479

If the problem persists when that is complete, the issue may be RPC over HTTP requests not completing.

A good test to know if RPC over HTTP requests can not complete is by enabling and disabling the MapiHttpDisabled registry setting, described here:  100040583.  If an Outlook session can connect to the system mailbox while the key is disabled, but not when the key is enabled, this is a strong indication that RPC traffic can not get to the Exchange destination.  EV's archiving tasks for Exchange 2013 and/or 2016 can ONLY use RPC over HTTP (displayed simply as "RPC" instead of "HTTP" as the protocol when viewed in the connection status of the Outlook icon in the systray) until version 12.2 or higher of EV.  Compatibility 

To overcome the potential causes of blocked RPC requests listed above, confirm:
1.  On the mailbox server, confirm that the feature RPC Over HTTP Proxy feature installed within the Windows Server Manager > Manage > Features console.  This ensures that RPC requests can be completed on that server.
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2.  From any machine that has the Windows Telnet client (this can also be installed from Server Manager), make a request to the Exchange server on port 6001.  Below is an example of a failed telnet connection, intentionally requested to the wrong port of 6002:
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3.  Use the hosts file on the EV server to allow requests to BOTH the Exchange Connection Point URL AND the autodiscover URL to bypass the load balancer. 

For example, make an entry for both of the above listed URL's to the IP address of one of the mailbox servers.  This is because both the Exchange Connection Point and the autodiscover URL's will be accessed when creating a mapi connection to the system mailbox.  The archiving task asks the Global Catalog (GC) for the autodiscover URL, and the autodiscover URL utilizes Windows Authentication to identify the VSA as an account that has access; thus eliminating the need for the task to provide credentials using RPC protocol. 

In this Example, is the Exchange Connection Point URL, and is the autodiscover URL.  The IP is the IP of an Exchange mailbox server.  After making this change, performing a tracert against the IP used can confirm that no hops to the load balancer are made.
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This applies for the third and fourth potential cause above.  If this allows RPC traffic through, and the use of the load balancer is desired, further research into the logging of the load balancer will be required to determine why traffic on 6601 or RPC traffic in general is not passed through. 

4. Set the MapiHttpDisabled registry setting to a value of 1.  This ensures that Outlook on the EV server can ONLY use RPC over HTTP as its protocol, and not Mapi over HTTP,  100040583.This registry key is required when targeting 2013 and 2016 Exchange servers, regardless of the configuration.

The goal of the above steps is to resolve RPC connectivity problems from EV to Exchange.  Once the conditions are met, an Outlook session should be able to connect as the VSA from the EV server to the system mailbox; without having provided any credentials, and only providing the Exchange server name and mailbox name - just as the EV archiving task would. 

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