What happens when a mailbox or your plan's storage is full

Applies to: Mailboxes included with your hosting plan (all plans).

A mailbox can run out of room in two ways: it reaches its own quota, or your hosting account as a whole runs out of disk space. Either way, new mail is refused until there is room again. This article explains what you and the people writing to you will see, and how to free up space.

When a mailbox reaches its quota

New mail is refused. Our server turns the message away while it is being delivered, so the sender gets a bounce with our reason in English: "Mailbox is full". The message isn't kept on our side: once there is room, the sender has to send it again.
Other mailboxes carry on as normal. Only the full mailbox refuses mail.
Your mail app may fail to save sent messages or drafts on the server, because they need space too.
Warnings come first. cPanel emails the mailbox itself when it reaches 80%, 90% and 98% of its quota. The warnings are in English.

When your plan's disk is full

Mailboxes share your plan's storage with your website files and databases. If your hosting account as a whole reaches its disk limit, every mailbox refuses new mail in the same way, even mailboxes far below their own quota. Your website is affected too: it can fail to save uploads, cache files or database changes. In cPanel, Disk Usage shows the account at or near its limit (see How to check your disk usage and file count).

Check how much space is used

Each mailbox: in the client area, Email Accounts shows each mailbox's usage and quota, and so does cPanel -> Email -> Email Accounts.
The whole account: Disk Usage in cPanel.

How to free up space

Get mail flowing again first. If the mailbox's quota is below your plan's maximum, raise it: in Email Accounts, open the mailbox's menu and change the quota (in cPanel: Email Accounts -> Manage). This works straight away. It doesn't help if your plan's disk is full; go on to the next steps.
Delete large messages. In webmail, sort your messages by size and delete what you don't need, saving any attachments you want to keep first.
Empty the Trash and Junk folders. Messages there still take up your plan's storage until you do.
Archive old mail on your computer. Most mail apps can move messages to a local folder on your computer, after which they no longer take up space on the server. Keep a backup of that computer: mail stored only there isn't covered by our backups.
If your plan's disk is full, remove old backups, logs, caches and unused files from the account (see How to check your disk usage and file count).
Delete mailboxes nobody uses any more. Deleting a mailbox deletes all its mail.

No automatic charges for extra storage

We never add paid storage automatically: a full mailbox simply refuses mail until there is room. If you regularly run short of space:

Raise mailbox quotas up to your plan's maximum per mailbox: 5 GB on Self-Managed Lite, 10 GB on Plus, Pro, Managed Starter and Growth, and 25 GB on Managed Business.
Move to a plan with more disk space. Our team makes the change on request: see How to upgrade or downgrade your plan.
Or ask us, and we'll look at the options with you.

If someone needs a very large mailbox, consider Professional Email (Microsoft 365 or Google Workspace), which keeps mail with Microsoft or Google, separate from your hosting: see How to add Professional Email to your hosting.

Troubleshooting this task

Mail bounces as full, but the mailbox is well below its quota. Your plan's disk is probably full. Check Disk Usage in cPanel.
You deleted mail, but the mailbox still looks full. Some apps only mark messages as deleted: empty the Trash, or use your app's option to compact or purge folders. cPanel also recalculates usage periodically rather than instantly, so give it a little time.
You can't raise the quota any further. The mailbox is already at your plan's maximum. Free up space as described above, or move to a larger plan.