If people tell you their messages bounced with "mailbox full" or "quota exceeded", your mailbox has run out of space and new mail can't be delivered. This guide explains how to fix mailbox full errors quickly, and how to stop them coming back.
What the error looks like
Senders usually get a bounce message containing something like:
552 5.2.2 Mailbox is full / Quota exceeded mailbox is full: retry timeout exceeded
You might also notice you've stopped receiving mail, or your mail app shows a quota warning. Messages sent while the mailbox was full are held for a while and retried; if the mailbox stays full, they're returned to the sender and won't arrive later. See How to Read a Bounce Message (Common Email Errors Explained) for more on reading bounces.
Step 1: Find which limit is full
There are two possible limits:
- The mailbox quota -- the size limit you set for that one email account.
- Your hosting account's disk space -- shared by your website, databases and all mailboxes. If this is full, every mailbox stops receiving.
To check:
- Log in to cPanel and go to Email > Email Accounts. The Storage column shows each mailbox's usage against its quota. A full or nearly full bar is the problem.
- Look at the Statistics panel on the right of the cPanel home page. If Disk Usage is at or near its limit, your whole account is full (see Understanding cPanel Statistics: Disk Space, Bandwidth and Databases).
Step 2: Free up space or raise the quota
If one mailbox is full
You have two choices, and you can do both:
- Delete old mail: go to Email > Email Disk Usage, pick the account, click Manage next to a large folder and delete old or large messages in bulk. Full steps are in How to Free Up Mailbox Space with Email Disk Usage.
- Increase the quota: go to Email > Email Accounts, click Manage next to the address, change Allocated Storage Space, then click Update Email Settings. See How to Change an Email Account's Storage Quota in cPanel.
If your whole account is out of disk space
Raising a mailbox quota won't help. Free up space across the account: clean out large mailboxes, delete old files and backups you uploaded to your website folders, and remove unused WordPress staging copies. If you've outgrown your plan, open a ticket to ask about more space.
Step 3: Test it
Send a message to the mailbox from another account (for example your phone's personal email). If it arrives, you're fixed. Let anyone whose mail bounced know they should send it again -- bounced messages aren't redelivered automatically.
How to stop it happening again
- Use IMAP sensibly: with IMAP all mail stays on the server, so tidy up now and then. Empty Trash and Spam regularly.
- Watch Sent mail: large attachments you send are stored in Sent. Share big files by link instead.
- Archive old mail: move mail older than a year or two into a local folder in your desktop mail app (and back that computer up).
- Give busy mailboxes room: set a realistic quota for addresses that get lots of attachments.
- Check your mail app's Trash settings: some apps never empty Trash unless you tell them to.
Common questions
Will I get the messages that bounced?
No. Once a message has bounced, it's gone from our side. The sender has to send it again. Messages that were only delayed (not yet bounced) will arrive once there's space.
I deleted lots of mail but it's still full
Deleted mail often sits in Trash, which still counts. Empty Trash. Usage figures in cPanel are also cached, so give it a few minutes before checking again.
Can I set a mailbox to unlimited?
You can choose Unlimited for the quota, but the mailbox is still limited by your Instant Access Internet Services hosting account's disk space. A very large mailbox is slower to search and sync, so a sensible limit is usually better.
Related guides
- How to Free Up Mailbox Space with Email Disk Usage
- How to Change an Email Account's Storage Quota in cPanel
- How to Read a Bounce Message (Common Email Errors Explained)
- Understanding cPanel Statistics: Disk Space, Bandwidth and Databases
- IMAP vs POP3: Which Should You Use?
Still stuck? Open a support ticket and the Instant Access Internet Services team will help.
