In Exchange 2013 you can set quota limits on individual mailboxes as wel as on databases. When you’ve set a limit on database level, the quota will be applied to all mailboxes on that database. When you’ve set quotas on individual mailboxes, generally these individual quotas will be leading. However, in some cases you may notice the user can send and receive email, even when they have exceeded their individual thresholds.
For example, I had this user, having a mailbox size of 920MB, though I had set a send limit of 340 MB. However, she was still able to send emails.
get-mailbox %username% | Select-Object DisplayName,ProhibitSendQuota,@{expression={(get-mailboxstatistics $_).TotalItemSize}}
In this case, I found the “UseDatabaseQuotaDefaults” value set to be $true. I ran the following command to find out:
get-mailbox %username% | Select-Object DisplayName,ProhibitSendQuota,UseDatabaseQuotaDefaults
When UseDatabaseQuotaDefaults is set to True, the DatabaseQuota will be leading. Individual quota’s are ignored.
You can change this setting to make sure individual settings are leading:
Set-Mailbox %username% -UseDatabaseQuotaDefaults $False
