What dead email addresses really cost

A dead address is a mailbox that no longer exists, or that nobody reads anymore: someone left the company, closed an account, or walked away from an inbox. You will often read that a list loses close to a quarter of its addresses every year, and that your email tool bills you for every one of them. The first half rests on shaky figures, and the second is mostly wrong. Dead addresses do cost money, just not where people think.

This guide works from the rules the tools publish themselves, checked on October 21, 2026, applied to a list of 10,000 addresses.

The bill is not the biggest cost

Most tools that charge by contact stop counting an address as soon as it hard bounces.

On these tools, a dead address that bounces soon stops weighing on the bill. What it costs is decided elsewhere: at the moment of that bounce, before it, and in your reputation.

First cost: one send can suspend the account

Sending platforms watch the hard bounce rate of every campaign, and several publish their threshold.

Brevo's rule targets the most common case exactly: a list you just imported. Take 10,000 addresses, imported and then sent to once, and assume every dead address hard bounces on that send.

With 3% dead addresses, one first send is enough to suspend a Brevo account. The price of that scenario is not a line on an invoice: it is a stopped campaign, an account blocked while the subscription runs, and, the second time, a tool you have to leave.

What a stopped campaign costs depends on what your campaigns bring in. Omnisend measured an average of $0.18 per scheduled campaign email across 2025, on the sends of the online stores that use it, or €0.16 at the European Central Bank reference rate of October 21, 2026 (1.1234 dollars for one euro): about €1,600 for one campaign sent to 10,000 addresses. That figure is typical of online stores, not of every list. To run the same numbers with your own list size, platform and campaign revenue, use the email bounce calculator: it starts from that estimate until you enter your own figure.

Second cost: a tier you pay for too long

Before the first send, nothing sets a dead address apart: it counts toward your total like a customer. Three rules make it cost longer than you would expect.

• HubSpot bills the higher tier until renewal. Going over your tier by a single marketing contact moves you to the next one, billed until your subscription's renewal date, even if your contact count drops in the meantime.
• MailerLite counts the whole cycle. An address that was active at any point in the billing cycle counts toward your limit, even if you delete it later.
• Mailchimp changes price at each contact tier. On the Standard plan, the 5,001 to 10,000 contact tier costs €121.36 a month, and the 10,001 to 15,000 tier €206.76, at the regular price after the first-year discount. Unsubscribed contacts count too, and going over your limit is billed.

A few hundred dead addresses can therefore move you up a tier, for a month at MailerLite and until renewal at HubSpot. Take a list of 10,300 addresses, 3% of them dead: with them, it sits in the 10,001 to 15,000 tier, while its 9,991 live addresses fit in the tier below. That is €206.76 instead of €121.36 a month on Mailchimp's Standard plan, and €109 instead of €79 for the billing cycle on MailerLite's Comfort plan. Removing them before the import means you never pay for them, not even once.

HubSpot, Klaviyo and Kit publish no contact tier price in euros, so this guide quotes none for them. HubSpot's pricing page in euros quotes seats, and its product catalog prices marketing contact tiers in US dollars only; HubSpot bills only marketing contacts, and a contact set as non-marketing stops counting at the next monthly update. Klaviyo's pricing page offers US or Canadian dollars, and Kit's quotes US dollars only.

Third cost: sends billed by volume

Brevo and Mailjet mainly bill a monthly email volume, not a number of contacts. Every email sent to a dead address uses up some of that volume, but only once: Brevo adds an address that hard bounced to its blocklist, and Mailjet then blocks sends to it.

The direct cost stays small: one email per dead address. What matters is the bounce rate of that first send, and the thresholds above.

Fourth cost: reputation, which never shows on the bill

Mailbox providers read your bounces as the sign of a poorly kept list. Validity, which measures deliverability for senders, says so in its 2026 report: a high level of unknown users sends negative signals, degrades your sender reputation and lowers the share of your email that reaches the inbox.

Dead addresses can also turn into traps. According to Spamhaus, some closed mailboxes reject mail for twelve months or more, then are silently turned back on as spam traps, and hitting one is a significant red flag. A list you have not written to for a long time therefore hides more of them than a list you send to regularly, whose bounces are already gone.

The mechanics are covered in why emails bounce.

Dead addresses that never bounce

Some dead addresses never bounce at all, so they stay on the bill with no end date.

• Catch-all domains accept mail for any address, real or not. PricklyMails marks them Review on the Pro plan and above; the guide on catch-all domains explains what to do with them.
• Abandoned mailboxes still exist and accept mail, but nobody reads them. No verification can tell: only engagement shows it, an address that has opened and clicked nothing for months.

For those, remove long-inactive subscribers on a regular schedule. Microsoft asks high-volume senders to Outlook to do exactly that: remove inactive or invalid addresses monthly or quarterly.

Where the 22.5% a year comes from

The most repeated figure, a list losing 22.5% of its addresses a year, or 2.1% a month, comes from a HubSpot page. HubSpot attributes it to MarketingSherpa research on B2B data, with no link, no year and no method, and we could not find the study. The other common figure, 23%, comes from ZeroBounce: it is the share of invalid addresses among everything its customers submitted in 2025, not the speed at which one list goes stale. People mostly verify the lists they doubt, which pushes that figure up.

The mechanisms, on the other hand, are documented. A Yahoo mailbox nobody opens for twelve months becomes inactive and stops receiving email. Google reserves the right to delete a personal account inactive for two years, and the first deletions have been possible since December 1, 2023. And in B2B, every person who leaves a company closes an address.

Measure your own list

Rather than a borrowed figure, measure yours. Verify about a hundred addresses picked at random from your list: you get an order of magnitude, not a precise measure, but you will know whether your next send is close to the thresholds above. If it is, verify the whole list before importing it, then follow each address's recommendation: send, review or remove.

The full method is in how to clean an email list, and the step by step for each tool on the Brevo, Mailchimp, HubSpot, Klaviyo and Mailjet pages.

For the sample, create an account: the tokens you get at signup cover about a hundred addresses, no credit card needed.