Account quotas apply to email messages, attachments and calendar appointments. When the quota is reached, all email messages are rejected. Users are not automatically notified.
Users will need to delete email messages and old appointments off the server to get below their quota limit, or you can increase their quota.
You can check account mailbox quotas from Server Statistics. The Mailbox Quota displays the following information for each account sorted by mailbox size in descending order. You can click on the Quota, Mailbox Size, or Quota Used headers to change the viewing order.
The Quota column shows the mailbox quota allocated to the account. Quotas are configured either in the COS or by Account.
The Mailbox Size column shows the disk space used.
The Quota Used column shows what percentage of quota is used.
Of a quota is not set, the Quota column displays 00.0MB. The account has unlimited use of disk space.