Hard Bounce
What is a hard bounce?
A hard bounce occurs when an email is permanently rejected by the recipient’s mail server. This means the email cannot be delivered, regardless of attempts.
Unlike temporary delivery issues, hard bounces occur due to reasons that cannot be fixed by simply retrying. These typically happen because of invalid email addresses, non-functional receiving servers, or typos in the recipient’s address.
To maintain good deliverability and protect sender reputation, email service providers usually stop sending emails to addresses that generate hard bounces.
Hard bounce vs. soft bounce: How are they different?
Understanding the difference between a hard bounce and a soft bounce helps maintain good email deliverability and protects your sender reputation.
Hard bounce: A hard bounce is a permanent delivery failure. This happens when the email address is invalid, the domain doesn’t exist, or the recipient’s server has blocked the sender. These addresses should be removed from your list.
Soft bounce: A soft bounce is a temporary delivery issue. Common causes include a full inbox, server downtime, or the message being too large. These emails may be delivered successfully in later attempts.
What are the common causes of hard bounces?
Invalid email address: The recipient’s email may be typed incorrectly or no longer in use. Even a small typo in the domain or username can lead to a permanent delivery failure.
Non-existent domain: The domain portion of the email (after the @) does not exist or cannot be reached.
Mailbox not found: The specific mailbox (username) does not exist on the recipient’s server.
Blocked by recipient server: The recipient’s mail server may have blocked emails from the sender permanently due to security or spam concerns.
Best practices to handle hard bounces
Keep email lists up to date and remove invalid addresses.
To minimize spelling errors, enable double opt-in so users can confirm and correct their email address before being added to your list.
Choose a service like ZeptoMail that automatically suppresses email addresses causing hard bounces, helping protect your sender reputation.
Monitor bounce reports periodically to identify issues quickly.
Use email validation tools to ensure that addresses are correct before sending campaigns.