550 Mailbox is full error: how to fix it

Introduction

The 550 Mailbox is full error means the server cannot deliver new messages because the recipient mailbox is full or has reached a related storage limit.

In some notices you may also see references to quota, blocks limit exceeded or inode limit exceeded.

What usually causes this error

The most common causes are:

• the mailbox has run out of available space
• the account exceeded its file or inode limit
• the domain or hosting plan reached its capacity
• too many old emails with heavy attachments are stored

Steps to fix it

1. Check whether the issue is on your side or the recipient side

If you get the bounce while writing to someone else, the problem is usually in the recipient mailbox.

If the error appears when receiving mail on your own domain, you need to review your local accounts.

2. Free space in the mailbox

Start by:

• emptying Trash
• emptying Spam
• deleting old attachments
• removing duplicate or very heavy messages

3. Check the mailbox quota

In cPanel or DirectAdmin, review the quota assigned to the email account and the actual mailbox usage.

If needed, increase the quota or reorganize storage.

4. Review inode or file-count limits

Even when the mailbox size in megabytes looks acceptable, an account with too many small messages can still hit the plan’s file limit.

5. Wait and test again

After freeing space, resend the email. If mailbox usage was the cause, the error usually disappears quickly.

Useful tips

1. Empty Spam regularly

   Many accounts keep filling up because unwanted mail is never removed.

2. Do not keep unnecessary attachments in email

   If you need them, download them and delete the message from the server.

3. Review quotas on shared addresses

   Accounts such as info@ or sales@ tend to fill up faster when several people use them.

Frequently asked questions

Does this error mean the server is down

No. It usually means the destination mailbox cannot accept more mail right now.

Can it be caused by inodes and not by megabytes

Yes. An account can be light in total size and still hit the file-count limit.

Will it fix itself

Only if someone frees space or increases the quota. Until then, the bounce may keep happening.

Conclusion

The 550 Mailbox is full error is usually fixed by reviewing space usage, quota and inode limits on the affected mailbox.

The sooner you clean the account or adjust its limits, the sooner normal email delivery will return.