Bounce Rate (Email)

Email bounce rate

Bounce rate tells you what share of the emails you sent never made it to the inbox: bounce rate = bounces / sent × 100%. Send 10,000 and have 200 bounce, and you're at 2.0%. A soft bounce is temporary, like a full mailbox, an out-of-office, or a server that's down. A hard bounce is permanent, like an invalid address or a domain that doesn't exist. Once you climb past roughly 3%, deliverability suffers, because Gmail and Outlook start docking your IP and domain reputation and routing the next sends to spam. A high bounce rate usually points to a dirty list: old leads, scraped addresses, no double opt-in. Pull hard bounces right away, and suppress soft bounces after a few failures in a row.

Applications

Cleaning and validating lists with NeverBounce, ZeroBounce, or Kickbox; keeping your ESP (Email Service Provider) reputation healthy on SendGrid, Amazon SES, Mailgun, and Postmark; getting SPF/DKIM/DMARC aligned; staying compliant with the U.S. CAN-SPAM Act and Brazil's LGPD; and running double opt-in so bots and typos never make it onto the list in the first place.

FAQ

Soft or hard bounce? A soft bounce is temporary and worth retrying; a hard bounce is permanent because the address is invalid. Most ESPs suppress hard bounces on their own and drop soft ones after N failures in a row.

What is an acceptable bounce rate? Under 2% is healthy. The 2–5% range is worth a closer look. Above 5%, the major providers see a red flag and may start throttling your IP.

How do I reduce bounce rate? Make double opt-in mandatory, clean the list on a regular schedule, never buy lists, and check addresses at signup with a real-time email-verification API.