When adding an email account via cPanel you will be asked to set a disk space quota. This represents the maximum amount of disk space that messages stored under the account can consume at any one time. This feature is very useful because it allows you to prevent a single email account under your domain from eating up the entire disk space quota assigned for the cPanel account.
If the disk space quota for an email account (or the cPanel account as a whole) is exceeded then messages sent to that email address will be queued on the server for a short period of time to see if disk space becomes available under the email account to allow successful delivery. If no space becomes available then the message will be bounced back to the sender to let them know that your account is over its disk space quota and no new messages can be received at the present time.
Resolving the issue
In order to resolve the issue you need to either free up some disk space under the account either by clearing the “spam” folder or by removing other messages or by increasing the overall disk space quota assigned to the account.
Could the problem be caused by Spam Box?
One very common reason for an account to reach its allocated disk space quota is if you have the “Spam Box” option enabled within cPanel. By using Spam Box it means that any messages sent to your account that the Spam Assassin system flags as being UCE / SPAM will be directed to the “spam” folder under your email account instead of to your inbox. If you do not clear the “spam” folder out regularly of your junk mail then it can rapidly grow in size and eat up your available disk space.
You can clear the “spam” folder either by:
1) Logging into cPanel, clicking the “Mail” menu, followed by “Spam Assassin” and then “Clear Spam Box”
– or –
2) Logging into web mail and clearing any UCE / SPAM messages contained within the “spam” folder of your email account. We advise using the second method as it allows you to check through the “spam” folder for any legitimate messages that may have been flagged by Spam Assassin as UCE / SPAM before removing them.
Checking your disk space usage and quota
You can check the disk space usage and the assigned quota for any individual email account by logging into cPanel, clicking the “Mail” menu, followed by “Manage / Add / Remove Accounts” and then “Show Disk Space Used”.
You can check the disk space usage and the assigned quota for a cPanel account as a whole by logging into cPanel and looking under the “general account information” section. If you have a Reseller Hosting or Premium Reseller Hosting plan you can also check the disk space usage and quota for each of your cPanel accounts by logging into the Web Host Manager (WHM) and clicking “Quota Modification”. This will list the assigned disk space quota and disk space usage for all of the accounts added under your reseller plan.
The following video demonstrates how to change an email account’s quota: