# Understand a bounce message

> Find out why an email you sent came back as undeliverable, and what to do next for each common reason.
>
> Source: https://docs.officeniaga.com/bounce-message/

A bounce is an automatic reply saying your email was not delivered. It often has a subject such as **Undeliverable**, **Mail delivery failed** or **Delivery Status Notification**, and the reason is written inside the message.

## Find the reason

1. Open the bounce message.
2. Look for the error line. It usually starts with a 3-digit code such as `550`, `552` or `554`, followed by a short explanation.
3. Match the explanation to one of the reasons below.

## Common reasons and what to do

- **Address does not exist or user unknown** - check the spelling of the address, or ask the person for the right one.
- **Recipient mailbox full** - the other person has no space left. Try again later, or contact them another way, such as by phone or WhatsApp.
- **Message too large** - send a smaller file, or upload it to Google Drive or OneDrive and send the link instead.
- **Rejected or blocked as spam** - see [Why your emails land in spam](/emails-going-to-spam/).

> **Tip**
> Attachments grow by about a third when they are sent, so a file that looks just under the limit can still be too large.

If your email never left your outbox at all, that is a sending problem, not a bounce. See [Emails won't send](/cannot-send/).

## None of these fit

Copy the whole bounce message, including the error line, and contact support on WhatsApp at [+60 16-916 3324](https://wa.me/60169163324). The full text helps us see exactly where delivery failed.

## Common issues

### Why did I get an email saying my message could not be delivered?

That is a bounce message. The receiving server rejected your email, and the reason is written inside the bounce. Open it and look for the error line.

### My email with a big attachment bounced. What should I do?

Upload the file to Google Drive or OneDrive and send a share link instead of the attachment.

### The bounce says the address does not exist, but I typed it correctly. Why?

The person may have left the company or changed their address. Ask them or their company for the right address, then send again.