By default, users or domains can exceed their quotas with no effect except for receiving an over quota notification (if set). Quota enforcement locks the mailboxes from receiving further messages until the disk usage is reduced below the quota level.
To enable or disable quota enforcement:
configutil -o store.quotaenforcement -v [ on | off]
Note that over quota messages are saved in the MTA queues and a notification is sent to the sender stating that their messages was not delivered, but that a redelivery attempt will be made later. Delivery retries will continue until the grace period expires and all messages are sent back to the senders, or the disk usage falls below the quota and messages can be dequeued from the MTA and delivered to the message store. If you want to return messages that are over quota before they get to the message queues, use the following command line:
configutil -o local.store.overquotastatus -v on
To Enable Quota Enforcement at the Domain Level
To enable for all domains exclude the -d option. When a domain exceeds its quota, the maildomainstatus attribute is set to overquota, which halts all delivery to this domain. If a domain is not overquota, the value is set to active.
Disabling Quota Enforcement
These configutil parameters should be off or not set:
Note that when local.store.overquotastatus is on, it always treats store.quotaoverdraft as on, otherwise the user will never go over quota to trigger the rejection. Also, when store.quotaoverdraft is on, the user is allowed one message which is smaller than the quota only. That is, it will never accept a message that is greater than the user’s quota.
After making changes to these parameters, be sure to restart your messaging services.
These Message Store attributes should be active:
Note that messages will bounce if they are larger than the mailbox quota, regardless of quota enforcement configuration.