How Bounce Rate Affects Your Email Sender Score (And How to Fix It)

Your sender score is like a credit rating for your email domain. A high score means your emails go to the inbox. A low score means spam folders or no delivery at all. Bounce rate is one of the strongest signals that affects it.

Hard bounces vs soft bounces

Hard bounces

A hard bounce means the email was permanently undeliverable: the address does not exist, the domain has no MX records, or the receiving server has rejected your domain. Remove hard bounces from your list immediately and permanently.

Soft bounces

A soft bounce means delivery failed temporarily: mailbox full, server temporarily unavailable, or message too large. Most ESPs automatically retry soft bounces. After 3-5 consecutive soft bounces from the same address, treat it as a hard bounce.

How ISPs interpret your bounce rate

Below 0.5%: healthy. 0.5-1%: borderline. 1-2%: concerning, list clean required. Above 2%: damaging, immediate action needed.

What drives high bounce rates

1. Old list with infrequent sending - email addresses decay at 22-25% per year
2. Purchased or scraped lists with poor data quality
3. No double opt-in allows typos and fake addresses to enter freely
4. No real-time validation at sign-up
5. Re-using old exports from 18 months ago

The fastest path to reducing bounce rate

1. Run a full list verification pass today
2. Add API validation to your sign-up forms
3. Enable double opt-in
4. Set up a re-engagement sequence for subscribers inactive for 12 months or more