How to Reduce Email Bounce-Backs
A bounce-back means your message did not reach the recipient. Understanding why helps you fix the cause and keep your sending reputation healthy.
Step-by-step
- Read the bounce message. It states the reason — "user unknown", "mailbox full", "message rejected as spam", etc.
- Distinguish hard from soft bounces. Hard = permanent (bad address) — stop sending to it; soft = temporary (full mailbox, server down) — it may retry.
- Correct bad addresses. "User unknown" means a typo or closed account — fix or remove it.
- Authenticate your domain. "Rejected as spam" often means missing SPF/DKIM — see SPF/DKIM and spam fixes.
- Use Track Delivery to see the exact server response for any address — see tracking delivery.
- Never bulk-send on shared hosting — it causes mass bounces and reputation damage.
💡 Good to know
- Repeatedly emailing a hard-bounced address harms your reputation — remove it.
- A sudden rise in bounces can mean a deliverability or blocklist issue worth investigating.
- Good authentication is the best long-term defence against rejections.