Outlook prompting for passwords due to server issue
One of the exchange database servers has 3 disks causing issues in a 4 disk array. This server has been taken out of the Exchange cluster pending a backup and rebuild/restore on the replacement disks.
Although the other servers can take the load, public folders have an affinity for their home server. When this is unavailable, they prompt for credentials while attempting to access it. This will not restrict the delivery of mail and the user can simply click cancel.
It will be a few days before the server is fully restored.