In Exchange Server 2010 as with Exchange Server 2007, all e-mail must go through a Hub Transport server before delivery to the mailbox. This is mainly to allow for compliance, but it also provides a means for data recovery.

Transport dumpster is a feature built into Exchange Server 2010 HUB transport role  and designed to minimize data loss during mail delivery to a DAG in a lossy failover scenario. This feature was first introduced in Exchange 2007 for CCR and LCR mailboxes.

The transport dumpster is used for replicated mailbox databases only. It doesn't protect messages sent to public folders, nor does it protect messages sent to recipients on mailbox databases that aren't replicated (not member of a DAG). The transport dumpster queue for a specific mailbox database is located on all Hub Transport servers in the Active Directory sites containing the DAG. The transport dumpster is stored inside the mail.que file. 

Exchange Server Transport Dumpster Settings

There are two settings that control the life span of a message within the transport dumpster. They are:

•MaxDumpsterSizePerDatabase   Defines the size available for each storage group on the Hub Transport server. The recommendation is that this be set to 1.5 times the maximum message size limit within your environment. The default value for this setting is 18 MB.

•MaxDumpsterTime   Defines the length of time that a message remains within the transport dumpster if the dumpster size limit is not reached. The default is seven days.

If either the time or size limit is reached, messages are removed from the transport dumpster by order of first in, first out. we can run the following command to see the current settings:

Get-TransportConfig |fl *Dumpster*

Changes in Exchange 2010

In Exchange 2007, messages were retained in the transport dumpster until the administrator-defined time limit or size limit is reached. In Exchange 2010, the transport dumpster now receives feedback from the replication pipeline to determine which messages have been delivered and replicated. As a message goes through Hub Transport servers on its way to a replicated mailbox database in a DAG, a copy is kept in the transport queue (mail.que) until the replication pipeline has notified the Hub Transport server that the transaction logs representing the message have been successfully replicated to and inspected by all copies of the mailbox database. After the logs have been replicated to and inspected by all database copies, they are truncated from the transport dumpster. This keeps the transport dumpster queue smaller by maintaining only copies of messages whose transactions logs haven't yet been replicated.

The transport dumpster has also been enhanced to account for the changes to the Mailbox server role that enable a single mailbox database to move between Active Directory sites. DAGs can be extended to multiple Active Directory sites, and as a result, a single mailbox database in one Active Directory site can fail over to another Active Directory site. When this occurs, any transport dumpster redelivery requests will be sent to both Active Directory sites: the original site and the new site.

In Exchange 2007 Microsoft Office Outlook Web Access (OWA) includes a feature to let users change their passwords. However, this feature requires that users log on to OWA to change their passwords. In a scenario in which a user password has expired, or in which users have to change their passwords when they first log on, users cannot log on to OWA to access the password change feature. Exchange 2007 SP3 adds a new feature to the Client Access server (CAS) role. This feature creates a new Internet Information Services (IIS) 7 module that detects expired passwords, and redirects users to a new change password page. By default, this feature is disabled. To enable the password reset feature, you must set a registry key.

To enable the password reset feature  

1.     Log on to the Exchange server that is running the CAS role by using an account that has local administrator rights.

2.     Start Registry Editor, and then locate the following registry subkey:

HLKM\SYSTEM\CurrentControlSet\Services\MSExchange OWA

3.     Create the following DWORD value if it does not already exist:

Value name: ChangeExpiredPasswordEnabledValue type: REG_DWORDValue data: 1

4.     Exit Registry Editor.

5. Perform IISReset.

The password reset functionality is enabled when ChangeExpiredPasswordEnabled is set to a nonzero (0) value. If this registry value is missing or is set to a value of zero, the password reset functionality is disabled.

Exchange 2010 SP1: Now that SP1 has RTM, it brings this feature to Exchange 2010, the password reset feature is not active by default.  To activate this feature in Exchange 2010 SP1, you will need to add the registry key above.

Exchange Server 2010 SP1 Beta incorporates a number of feature updates including: archiving and discovery enhancements, a faster Outlook Web App (OWA), upgraded mobility features, and several improvements in the management UI. The SP1 beta is available to the public and can be downloaded

http://www.microsoft.com/downloads/details.aspx?FamilyID=a0965fc9-2723-4947-ae6b-74bc3808e72a&displaylang=en

In Exchange 2010 none of the preloaded role groups have the Mailbox Import Export role, The person performing the import or export must have the appropriate permissions within Exchange. The easiest way to grant this permission is by adding  Mailbox Import Export role to a role group.

To create the role group we need to run the following:

New-RoleGroup "Mailbox Import-Export Management" -Roles "Mailbox Import Export"

This will create a group called “"Mailbox Import-Export Management"”, every user added to this group will have the right to run the import/export cmdlets, adding a user can be done by running the following:

Add-RoleGroupMember "Mailbox Import-Export Management" -Member <user account>

If you try to run the cmdlets and you don't have the correct permissions, you'll receive an error stating that the cmdlet doesn't exist. And by the way , you'll need to restart the Exchange Management Shell after you add the Mailbox Import Export role to the role group.

The KB is http://support.microsoft.com/?kbid=982639 

Download from here http://www.microsoft.com/downloads/details.aspx?FamilyID=09b4973e-3a80-4fb9-9f60-5c6e2b7a2727&displaylang=en

By the way Exchange 2007 SP2 is at Update Rollup 4 : http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=b8f7f872-16d5-49d6-9867-adc01351c06f