Quick summary
- What it is: A bounce (or email bounce) is the automatic error message you receive when an email you sent could not be delivered to the recipient.
- What it's for: it helps configure, send, receive and protect email for a domain.
- When to check it: when creating email accounts, configuring an email client or investigating sending and receiving issues.
A bounce (or email bounce) is the automatic error message you receive when an email you sent could not be delivered to the recipient. It is the mail server's notification saying "this message did not reach its destination, and here's why".
Types of bounce
There are two main types, with very different implications:
- Hard bounce (permanent bounce): The email could not be delivered due to a definitive reason that will not change. The most common causes are that the email address does not exist, the domain does not exist or the server permanently rejects emails from that sender. Recommended action: remove that address from your mailing lists.
- Soft bounce (temporary bounce): The email could not be delivered due to a temporary reason that can be resolved. Common causes are that the recipient's mailbox is full, the mail server was temporarily unavailable, or the message was too large. Recommended action: the server will attempt automatic resending for a period of time.
Why are bounces important?
A high bounce rate, especially hard bounces, can:
- Damage the reputation of your server's IP and cause your domain to end up on a blacklist.
- Cause your email or hosting provider to suspend the email service for abuse.
- Indicate that your contact lists are outdated or contaminated with fake emails.
Typical bounce message
When a bounce occurs you receive a notification email with an error code. The most common ones:
550 5.1.1: The mailbox does not exist.550 5.7.1: The message was rejected by spam filters or blacklists.452 4.2.2: Mailbox full (soft bounce).
When will you encounter it?
Bounces appear in your email client history (Outlook, Thunderbird, Webmail) when you send emails to incorrect addresses. You will also see them in server logs if you have access to the control panel, and in notifications from email marketing tools when a campaign generates many bounces.
Why it matters in hosting
Understanding this concept will help you make better decisions when managing your service. In practice, it relates to configuring, delivering, receiving and protecting email for a domain. If it appears in a guide, the control panel or a support response, review the context before making changes.
Related articles
- Webmail
- IMAP
- POP3
- SMTP
- SPF