When troubleshooting mailbox switch and mail routing problems it's important to know how mail redirectors are set before and after mailbox switch.
NOTE: The following is for Onprem to Onprem Migrations
For example:
Using the Exchange template address @source.local and @target.local (refer to QMM Quick Start Guide). There is user object User01 migrated to the Target. After the full sync is ran, User01@source.local is stamped in the ProxyAddresses attribute on Source and Target objects. The targetAddress attribute on the Target User is set to User01@source.local for Mail Redirection to the Source Mailbox.
BEFORE MAILBOX SWITCH:
SOURCE: ProxyAddresses contains secondary smtp=User01@source.local
TargetAddress=<Not Set>
TARGET: ProxyAddresses contains secondary smtp=User01@source.local
TargetAddress=User01@source.local
IMPORTANT: In Exchange 2007 target scenarios the @source.local template will not be present on the target object. This is absolutely normal and has no effect on correct mail routing before or after mail switch.
When switching mailboxes the following step by step operations can be traced in the log file:
Applying changes ...
Updating object: <GUID=82D18772EA168D418EE765DE96AAAB76> (SOURCE MAILBOX)
Applying attributes:
targetAddress=smtp:User01@target.local
Applying changes ...
Updating object: <GUID=0B7982B4569D72469EF7D6EC0C45C492> (TARGET MAILBOX)
Applying attributes:
proxyAddresses=smtp:User01@target.local
targetAddress=
From this example, you can see how User01@target.local redirector is set on Source Object and the same value is added to ProxyAddresses attribute on the Target Mailbox while the targetAddress attribute is cleared.
AFTER MAILBOX SWITCH:
SOURCE: ProxyAddresses contains secondary smtp=User01@source.local
TargetAddress=User01@target.local
TARGET: ProxyAddresses contains two secondary addresses: smtp=User01@source.local; smtp=User01@target.local
TargetAddress=<Not Set>
Refer to Microsoft Article: "TargetAddress Property": http://msdn.microsoft.com/en-us/library/Aa487600
"Messages sent to any of the addresses specified by the ProxyAddresses Property will actually get delivered to the one specified by the TargetAddress property. The primary address in the ProxyAddresses list appears on the reply-to line of messages sent from this recipient."
