I'm designing a multiple database Exchange Server solution for a small company with a very strict 2-hour recovery service level agreement (SLA). I'll configure one storage group (SG) with five databases on one Exchange system. If one of those databases dismounts in a recovery situation, will internal email sent to a user's mailbox in the dismounted database queue on the server or bounce as undeliverable?
As long as the SG is active, Exchange will accept mail addressed to a user's mailbox in a dismounted database without generating a nondelivery report (NDR) and will attempt to deliver the mail after the administrator or Exchange has remounted the database. If the database remains dismounted for more than the defined time limit for holding mail (the default is 2 days), Exchange will return the mail as undeliverable. Remember that you can back up or restore only one database in an SG at one time. Make sure that you can still meet the 2-hour SLA if you have to restore more than one database at a time.