If Enterprise Vault services weren't stopped while Active Directory schedule maintenance stop, Enterprise Vault will generate some errors while Active Directory maintenance period such as authentication failure for Exchange server connection and/or SQL server connection. After Active Directory resume its service, Enterprise Vault may cause some issues even though Enterprise Vault is designed to restore these connections automatically. The reason why automated recovery doesn't work 100% isn't identified.

Workaround: Symantec recommend to stop all Enterprise Vault services and tasks on Active Directory maintenance stop to prevent such unexpected problems, or restart all Enterprise Vault services after Active Directory maintenance stop period.