Considerations for migrating mailboxes with quotas (4285270)

This article describes considerations for migrating mailboxes with quotas enabled.

Mailbox quotas are stored in 4 Active Directory attributes:

The Directory Sych (DSA) will synchronize all 4 of these attributes by default.

Important note:  It has been observed that how mDBUseDefaults is interpreted when it is differs between Exchange versions.  Exchange 2007 and 2010 will treat it as equivalent to TRUE whereas Exchange 2013 will treat it as FALSE.

Some points to remember:

1. Exchange 2007/2010 have default quotas enabled by default on the Mailbox Databases.
2. If you do not want to bring your quota settings to the target environment, you can skip these attributes in your DSA Synch settings. You will need to enable the Advanced Attributes to view these in the Skip Attributes Dialog. Skipping the mDBUseDefaults attribute will result in no value being set to mDBUseDefaults by DSA. Interpretation of this differs between Exchange versions, please see important note above
3. If the mDBUseDefaults attribute is FALSE in source but not skipped during sync, and individual quotas have been set, but the mDBStorageQuota, mDBOverQuotaLimit, and mDBOverHardQuotaLimit are skipped, then the mDBUseDefaults attribute will be set to FALSE in the target, however since mDBStorageQuota, mDBOverQuotaLimit, and mDBOverHardQuotaLimit will be blank, the result is that the user will have an unlimited Quota
4. Ensure source user accounts are out of sync scope before deprovisioning mailboxes as mDBUseDefaults will be set to causing the Store Default Quotas to be enforced.

If you need to reset a users quota, the following powershell command will work (note you can replace unlimited with a quota size in KB):

Set-Mailbox -UseDatabaseQuotaDefaults:$False -issuewarningQuota “UNLIMITED” -ProhibitSendQuota “UNLIMITED” -ProhibitSendReceive “UNLIMITED”

to retrieve users not using database defaults

get-mailbox -filter {usedatabasequotadefaults -eq $false -AND recipientTypeDetails -eq 'usermailbox'}

Cmdlet to set/remove use storage defaults

get-mailbox -filter { usedatabasequotadefaults -eq $false -AND recipientTypeDetails -eq 'usermailbox'} | set-mailbox -UseDatabaseQuotaDefaults $true/$false