in this SBS2011 installation with very few users, quotas are disabled. If I ask powershell for active quota, I get:
[PS] C:\Windows\system32>Get-Mailbox username| fl *Quota
ProhibitSendQuota : unlimited
ProhibitSendReceiveQuota : unlimited
RecoverableItemsQuota : unlimited
RecoverableItemsWarningQuota : unlimited
IssueWarningQuota : unlimited
RulesQuota : 64 KB (65,536 bytes)
ArchiveQuota : unlimited
ArchiveWarningQuota : unlimited
Still the user daily receives notification, that his mailbox is almost full.
Database quota are also disabled.
Where to look?