Fixing the "Mailbox is Full" Error in cPanel Print

When your email account matches or exceeds its maximum storage quota, inbound senders will receive a bouncing message reading "552 Message rejected: Mailbox is full" and you will be unable to send outgoing mail. This guide explains how to clear old data from your mailbox to restore service.

Step 1: Check your Active Mail Usage

1. Log into cPanel.
2. Open the Email Disk Usage utility within the Email section.
3. Select the specific address experiencing issues from the account dropdown menu.

Step 2: Clean up Mail Directories

The tool displays a breakdown of storage space by directory (Inbox, Sent, Trash, Spam). To manage large volumes of old messages:

1. Locate the target directory folder layout and click the blue Manage control hyperlink on the far right.
2. Under the deletion filter option panel, choose an action:
   • 1 year or older (Removes old archival logs safely)
   • 30 MB in size or larger (Targets messages with heavy video or file attachments)
   • All messages (Useful for clearing out the Trash or Spam folders completely)
3. Click Delete Permanently to clear the selected files.

Step 3: Increase the Mailbox Account Quota

If you don't want to delete any messages, you can increase your total account quota instead (if your hosting plan has available space):

1. Go to cPanel and open Email Accounts.
2. Click the Manage button situated next to your target email address.
3. Scroll down to the Storage area and adjust the quota number upward, or check the Unlimited setting.
4. Click Update Email Settings.