You could also use EVPM to relink an archive to a mailbox. Search the forum, I have already coverd it many times :)
Information about relinking:
Appendix B– Ensuring Mailbox / Archive Association
Definitions:
• Mailbox GUID – This is the unique ID for the mailbox, used by Exchange and stored in Active Directory.
• Hidden Message – This is a MAPI document placed in the users mailbox (in the root and hidden from a normal users view) that contains, amongst other information, that mailbox’s archive ID, its Enterprise Vault home server, the archiving policy applied to the mailbox and which archiving
buttons and functionality to show the user. This document is updated every time the mailbox is synchronized.
When moving a mailbox between Exchange environments that are serviced by the same Enterprise Vault archiving infrastructure, Enterprise Vault will attempt one of a number of actions on the newly migrated mailbox in order to re-link it with its existing archive. The successful action depends on
whether the migration process (and tools used in the process) allowed the mailbox to keep the same GUID and /or the same Enterprise Vault hidden message. Table below summarizes the options:
Mailbox GUID Legacy MailboxDN Re-link behavior
Preserved Preserved Mailbox automatically re-linked by the provisioning task
Preserved Not Preserved Mailbox automatically re-linked by the provisioning task
Not Preserved Preserved Admin intervention required. Use of the SynchInMigrationMode registry value (see below)
Not Preserved Not Preserved Admin intervention required. Manually specify the archive to use for each migrated mailbox.
SynchinMigrationMode registry key:
Name: SynchinMigrationMode
Path: HKLM\SOFTWARE\KVS\Enterprise Vault\Agents
Value:
0 (Issue Warnings for migrated mailboxes, but do nothing)
1 (Assigned newly migrated mailboxes to existing archives based on matching their LegacyMailboxDN)
2 (Do not assign newly migrated mailboxes to existing archives, instead create new archives).