In a newly deployed Exchange 2013 with the latest Cumulative Update 5 on POA 5.5.x, OAB is not generated on the Mailbox server and the following error can be seen in Event Viewer:
Generation of OAB "\S000000019 OAL" failed.
S:Exp=System.DivideByZeroException: Attempted to divide by zero.
Zero values for OABGeneratorWorkCycle and OABGeneratorWorkCycleCheckpoint properties of the mailbox servers configured by POA cause Exchange 2013 CU5 fail to generate OABs with the "divide by zero" error.
To fix this problem, the following cmdlet should be executed in Exchange Management Shell on any Exchange 2013 Mailbox server:
$timeSpanMax = [TimeSpan]::MaxValue; Get-MailboxServer | Set-MailboxServer -OABGeneratorWorkCycle $timeSpanMax -OABGeneratorWorkCycleCheckpoint $timeSpanMax