Some time ago, I came across a rather interesting technote. The technote offers a way how you can continue archiving for mailboxes with a disabled active directory account. This can be interesting to be activated when there is someone leaving the company and all his mails need to be stored in the archive.
The text below is a copy-paste from the Symantec Enterprise Support site.
By default, Enterprise Vault (EV) does not synchronize mailboxes associated with disabled AD accounts.
To override this behavior:
1. Create the following registry value on each EV server with a Mailbox Archiving Task:
For OS in 32 bits:
For OS in 64 bits:
DWORD Value: ExcludeDisabledADAccounts
Value data: 0
2. Restart all Mailbox Archiving Tasks on each EV server to apply this change.
Enterprise Vault will now attempt to synchronize mailboxes regardless of whether they are associated with a disabled AD account. Should a synchronization attempt fail, an error is recorded in the EV event log.
NOTE: Removing this value from the registry or changing the value to ‘1’ will revert to the default behavior.