How to Fix "Mailbox is Full" Error in cPanel

When your email mailbox reaches its storage limit, new emails will be rejected with a "Mailbox is full" or "Quota exceeded" message. Senders receive a bounce-back email saying delivery failed. This guide explains how to free up space and increase your quota.

Step 1: Check Your Mailbox Usage

1. Log in to your cPanel account.
2. Go to Email → Email Accounts.
3. Find your email address and check the Usage column.
4. If it shows 100% or a red bar, your mailbox is full.

Step 2: Free Up Space

Method A: Delete Large Emails in Webmail

1. Click Check Email next to your email address to open Roundcube.
2. Sort emails by size — look for emails with large attachments.
3. Select and delete emails you no longer need.
4. Important: also empty your Trash and Spam folders — deleted emails still count toward your quota until they are permanently removed.
5. Right-click the Trash folder → Empty. Do the same for Spam.

Method B: Delete Emails with Large Attachments via cPanel

1. In Email → Email Accounts, click Manage next to your address.
2. Go to the Storage section to see which folders are using the most space.
3. Use this information to target specific folders in webmail.

Step 3: Increase Your Mailbox Quota

1. Go to Email → Email Accounts.
2. Click Manage next to the email address.
3. Under Storage, change the quota to a higher value (e.g., 5000 MB or Unlimited if your plan allows).
4. Click Update Email Settings.

Step 4: Prevent Future Issues

• Set up email filters to auto-delete or auto-archive old emails: go to Email → Email Filters.
• Regularly empty your Trash and Spam folders.
• Save large attachments to your computer and delete the email.
• Consider archiving old emails: download them as .eml files for offline storage.

Important Notes

• Even after deleting emails, the quota update can take up to 15 minutes to reflect.
• Emails in the Trash and Spam folders count toward your quota. Always empty these folders.
• Some email clients (Outlook, phone apps) keep a local cache. Even after deleting from webmail, the client may still show old emails until it re-syncs.
• If your hosting plan has limited disk space, an "Unlimited" quota still uses your overall cPanel disk space.

Troubleshooting

• Deleted emails but quota is still showing full: Empty the Trash and Spam folders in Roundcube. The quota may also take 10-15 minutes to update after deletion.
• Cannot increase quota: Your hosting plan may have a maximum per-account email quota. Check your plan details or contact support for a quota increase.
• Quota says unlimited but still getting bounce-backs: Your cPanel account's total disk space may be full, not just the mailbox. Check your total disk usage in cPanel (right sidebar or "Disk Usage" section).
• Senders get "user over quota" bounce but I can still receive some emails: New emails may be arriving but are smaller than the quota buffer. Larger emails are being rejected. Free up space immediately.
• Don't know what is using the space: In Roundcube, hover over each folder to see its size. The Sent folder is often the culprit — set it to auto-delete emails older than 90 days.

Need help? Contact our support team.