WTF Series
WTF is Bounce Rate?
The percentage of your emails that get rejected outright. Hard bounces are permanent. Soft bounces are... complicated.
The real explanation
When an email bounces, it means the receiving server refused to accept it. Hard bounces are permanent rejections: the address doesn't exist, the domain is dead, or the server flat-out refuses your mail. Soft bounces are temporary: the mailbox is full, the server is down, or you're being rate-limited. That's the textbook definition. Here's the messy reality.
Soft bounces are way more complicated than anyone tells you. Some ESPs retry soft bounces automatically. Some don't. Some count a soft bounce after one attempt, others after five. And here's the part that catches people: an address that soft bounces every single time you send is basically a hard bounce, but your ESP might keep it "active" in your list because it's technically temporary. You end up sending to dead addresses for months.
The benchmark: keep your hard bounce rate under 2%. If you're above that on a single send, something is seriously wrong with your list. For soft bounces, watch for patterns. An address that soft bounces three or more times in a row should be treated as a hard bounce and removed.
Show me an example
You upload a list you haven't mailed in 8 months. 6% of the addresses hard bounce because people changed jobs, closed accounts, or let domains expire. Your bounce rate spikes, your sender reputation takes a hit, and your ESP flags your account. Meanwhile, 300 addresses have been soft bouncing every send for the past 5 months, but they're still in your "active" list because nobody set up rules to auto-suppress repeat soft bounces.
Who handles this?
Petros covers list hygiene.
Go deeper
Read more in the Email Almanac: Bounce Rate in the Almanac
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