Hard Bounce
A hard bounce is a permanent email delivery failure where the recipient address is invalid, doesn't exist, or the receiving server has permanently rejected the message.
What Is Hard Bounce?
Hard bounces occur when an email address is misspelled (e.g., john@gmial.com), the account has been deleted, or the domain doesn't exist. Unlike soft bounces, hard bounces will never resolve on their own — sending to the same address again will always fail. ISPs track hard bounce rates closely, and a rate above 2% can trigger deliverability penalties. Every hard bounce is a signal to email providers that you may not be following proper list management practices.
Why It Matters for Newsletters
Each hard bounce counts against your sender reputation. Continuing to send to addresses that hard-bounce tells ISPs that you're either using a purchased list or not maintaining proper list hygiene. This can result in your entire sending domain being flagged, affecting delivery to all your valid subscribers.
Best Practices
- Remove hard-bounced addresses immediately — never retry them
- Implement email validation at signup to catch typos and invalid formats
- Use double opt-in to confirm addresses are real and active
- Audit your list if hard bounce rate suddenly spikes — it may indicate a data quality issue
How Aldus Handles This
Aldus automatically removes hard-bounced addresses after the first occurrence. You'll never accidentally send to an invalid address twice, and your bounce rate stays well within healthy limits.