What’s the recommended maximum tolerance for invalids?
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You send a campaign, and a chunk of emails bounce straight back as undeliverable. Not soft bounces from a full inbox. Hard bounces from addresses that simply don't exist. That's your invalid rate, and it tells you a lot about how healthy your list really is.
The widely accepted threshold is below 2% of your sent volume. Best practice puts that target closer to under 1%. If you're regularly hitting 2% or higher, something upstream needs fixing, whether that's your sign-up form, your confirmation flow, or how old your list has gotten.
New addresses are where this gets interesting. A freshly collected address should not bounce. If you're seeing high invalids on recent sign-ups, that's a signal worth acting on quickly. Common culprits are typos at the point of entry (think "gmial.com" instead of "gmail.com"), fake submissions from people who'd rather not share their real address, or disposable addresses that were already dead on arrival.
High invalid rates hurt your sender reputation because mailbox providers treat repeated invalid sends as a sign you don't maintain your list responsibly. It also just wastes your send budget on addresses that will never convert.
If your invalid rate has crept up, a one-time list clean is usually the fastest fix. We do that at RME if you want a hand (no spreadsheet wrangling on your end).
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