Cold email bounce rate

Cold email bounce rate is the percentage of sent emails that couldn't be delivered. A hard bounce means the address doesn't exist; a soft bounce means a temporary problem like a full mailbox or a server timeout.

Hard bounces are the ones that hurt. Every mailbox provider treats a sender who keeps hitting dead addresses as someone working a stale or scraped list, and reputation drops with each one. Soft bounces are noise unless they repeat.

The number to watch is hard bounces as a share of sends. Under 2 percent is clean. Above 5 percent, Google and Microsoft start throttling the domain, and above that it gets worse quickly. The fix isn't in the copy. It's in verifying every address before it's sent to, and removing anything that bounced from every future list.

An example

A program sends 1,000 emails in a week. Fourteen hard bounce and nine soft bounce. The hard bounce rate is 1.4 percent, which is fine. The next week the same program sends to a list someone exported from a database without verifying it, and 68 of 1,000 hard bounce. That's 6.8 percent, the domain gets throttled at Gmail within days, and the good emails in the same batch start landing in spam.

How to measure it

Hard bounces divided by sends, per domain, per week. Track it by domain rather than for the program as a whole, because one bad domain can be pulled while the others keep sending.

Related terms

Email deliverability · Sending domain · Spam complaint rate · Email warmup

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