UPDATE (7/29/15 11:34am): Self-provisioning of Exchange mailboxes through the ADadmin web app may fail with a error code 12. If a mailbox is needed, please submit a request through 4help. No ETA for fix.
UPDATE (7/28/15 8:10am) : The exchange reboots last night did not fix the issues - there is an open issue call with Microsoft going on now.
VT Exchange mailbox creation is currently unavailable. Due to configuration issues with a cumulative update (CU) we are currently experiencing failures in provisioning through our ADadmin web app. Users attempting to create a mailbox in ADadmin will receive a “Error 12” or similar message. An emergency reboot tonight will hopefully resolve this issue. More information when available.