All failed tasks experiencing this issue will log the Event ID 3305:
Event ID: 3305
Description:
The Task '<Archiving Task>' failed to log on to Exchange server '<servername>' using mailbox 'mailbox@domain.com'.
Please ensure that the server is running and that the Vault account has sufficient permissions on the server.
V-437-3305
If a Mailbox Archiving Task is configured then the event ID 2256 will be logged:Event ID: 2256
Description:
The Archiving task '<Mailbox Archiving Task>' could not be started due to startup errors.
V-437-2256
If a Journal Task is configured then the event ID 2258 will be logged:
Event ID: 2258
Description:
The Journal Task '<Journaling Task>' could not be started due to startup errors.
V-437-2258
If a Public Folder Task is configured then the event ID 2949 will be logged:
Event ID: 2949
Description:
The Public Folder Task '<Public Folder Task>' could not be started due to startup errors
V-437-2949
{CMailboxHelper::OpenMailbox:#335} Opening message store...
{CMailboxHelper::OpenMailbox:#344} Could not open message store: [0x8004011d]
{CMAPISession::CreateMapiSession:#397} Releasing exclusive profile lock following error [0x8004011d]