Question

Is it possible for server A to access a private queue from server B?

Answer 1

There is little functional difference between a public and private queue, except that MSMQ publishes information about public queues in Active Directory (AD).

I’ve never done this myself, but it appears that if you know the full path to the private queue, you can access it from another server:

Private queues

Private queues are queues that are not
published in Active Directory and are
displayed only on the local computer
that contains them. Private queues
have the following features:

Message Queuing registers private
queues locally by storing a
description of the queue in the LQS
(local queue storage) directory on the
local computer. In MSMQ 2.0, and
Message Queuing 3.0, the default
location is
%windir%\system32\msmq\storage\lqs.
Note that a description of each public
queue created on the local computer is
also stored locally in a separate file
in the LQS folder.

Private queues are registered on the
local computer, not in the directory
service, and typically cannot be
located by other Message Queuing
applications.

Private queues are accessible only
by Message Queuing applications that
know the full path name, the direct
format name, or the private format
name of the queue, as follows:

Path
name:ComputerName\private$\QueueName.

Path name on local computer:
\private$\QueueName.

Direct format name::
DIRECT=ComputerAddress\PRIVATE$\PrivateQueueName.

Private format name:
PRIVATE=ComputerGUID\QueueNumber.

For more information on path names and
format names, see Queue names.

Private queues have the advantage of
no directory service overhead, making
them quicker to create, no latency in
accessing them, and no replication
overhead.

Private queues are not dependent on
the directory service, and thus can be
created and deleted when the directory
service is not working. This is useful
for offline operation.

One way that private queues can be
exposed to other applications is by
setting a message property. To
distribute the location of a private
queue, an application can send a
format name of the private queue as
the response queue property of a
message.

Ref.