Email Sent Message Error: 550 Mailbox Quota Exceeded

One common bounced back email error message when sending email

is: 550 Mailbox quota exceeded. It means the recipient is not able to accept the message because of their full inbox.

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Email fails with the following error message.
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Subject: Mail delivery failed: returning message to sender
'mailbox is full: retry timeout exceeded'

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Reasons for the error message:
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Following are the possible reasons for the error message:

1. The disk quota exceeded for the email account.
2. Disk quota for the particular domain exceeded.

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Possible Solutions:
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If your email address has used the allowed quota, there are a few ways to correct this.  First, you could simply delete some of your emails. Deleting emails in your email client will remove them from the server and lower the space used. If you have any emails with large attachments, deleting those will free up space.

Steps to increase the quota for an email account:

Step 1) Login to the cPanel of the domain using your domain name as follows :

==> http://www.yourdomain.com:2082    or
==> http://www.yourdomain.com/cpanel   or

Step 2)  Next, navigate to the "Email Accounts" under "Mail" section. In the following page, we can see the list of email accounts existing under that domain. Increase the quota for the email account by clicking "Disk & Quota" and changing it to the required value.

If the disk quota of the email account is not causing the issue then the quota limit for the domain might be exceeded.

Steps 3) Please check If any of your email accounts are over quota, they will show in red. Either you can delete the unwanted files or you can increase the quota of the domain.

Steps 4) To raise the quota, click on "Change Quota" under actions shown in cPanel

Steps 5)  Raise the number in the "Mailbox Quota" field and click Change Quota.  Now, as you can see the quota has raised and the address no longer shows as red.

You can use this method to raise the quota on any email account. If any inboxes are close to full, you can raise the quota to avoid a future issue.