Hard bounce

What is a hard bound?

An email hard bounce occurs is when the delivery issue is permanent, such as an invalid email address.

You’ll see a hard bounce notification code that starts with a “5xx.”

Unlike a soft bounce, a hard bounce should be considered permanent.

Common reasons for a hard bounce include

A hard bounce in email delivery refers to a permanent failure to deliver an email to the recipient. Unlike soft bounces, which are often temporary issues, hard bounces indicate persistent problems. Common reasons for email hard bounces include:

• Invalid Email Address – the recipient’s email address is incorrect, misspelled, or doesn’t exist.
• Domain Doesn’t Exist – the domain part of the email address (after the “@” symbol) doesn’t correspond to a valid and existing domain.
• Recipient Email Server is Down – the recipient’s email server is not operational, preventing the delivery of emails.
• Blocked Email Address – the recipient has marked the sender as spam, or the email address is on a blacklist, resulting in blocking.
• Email Size Exceeds Limit – the email is too large and exceeds the maximum size limit allowed by the recipient’s email server.
• Recipient Mailbox Full – the recipient’s email inbox has reached its storage limit, and no more emails can be accepted until space is cleared.
• Invalid Recipient Mail Server – the recipient’s email server is misconfigured or not accepting emails.
• Syntax Errors in Email Address – the email address contains syntax errors, making it impossible to deliver the message.
• Email Content Issues – the email content violates the policies of the recipient’s email service provider, leading to rejection.
• Email Account Closed – the recipient’s email account has been closed or deactivated.
• Role-Based Email Addresses – some email providers reject emails sent to role-based addresses (e.g., [email protected]) to prevent spam.

Hard bounces negatively impact email deliverability, and a high rate of hard bounces may lead to an email sender being marked as a potential source of spam. Maintaining a clean and regularly updated email list, using double opt-ins, and following best practices for email marketing can help reduce the occurrence of hard bounces.