Email List Health Report 2026
Nearly 1 in 3 addresses on lists uploaded for cleaning was undeliverable.
461,457 addresses from Verifox customers, July to November 2026.
Key finding
Of 272,780 addresses on lists customers uploaded to Verifox for cleaning between October 12 and November 8, 2026, 31.9% were undeliverable and another 25.9% were risky. Only 39.5% were safe to send. Addresses checked one at a time were cleaner, but 19.3% of those still failed.
31.9%
of addresses on uploaded lists were undeliverable
39.5%
of addresses on uploaded lists were safe to send
33.8%
of free-mail addresses checked one at a time failed, vs 15.7% of business addresses
10×
more catch-all addresses on Google-hosted mail than on Microsoft-hosted mail (23.3% vs 2.3%)
Only 4 in 10 addresses on uploaded lists were safe to send
When people upload a list for cleaning, they are usually about to send to it. On those lists, 31.9% of addresses were undeliverable: the domain had no mail server, or the receiving server said the mailbox does not exist or is disabled. Another 25.9% were risky, which means the server accepted mail but the mailbox could not be confirmed. That leaves 39.5% that were safe to send.
Addresses checked one at a time, through signup forms, the API, AI agents and single lookups, were cleaner. Even so, 19.3% failed and 12.1% were risky.
| Verdict | Lists uploaded for cleaning | Checked one at a time |
|---|---|---|
| Undeliverable | 31.9% | 19.3% |
| Risky | 25.9% | 12.1% |
| Unknown | 2.6% | 6.7% |
| Safe to send | 39.5% | 61.9% |
| Addresses | 272,780 | 188,677 |
| Customer accounts | 157 | 256 |
Business email is cleaner, but 1 in 6 addresses still failed
Among addresses checked one at a time, 15.7% of addresses on business domains were undeliverable, against 33.8% of free-mail addresses such as Gmail, Yahoo and Outlook.com. Free-mail made up 19.7% of those checks. A work address is a better bet than a personal one, but it still needs checking: roughly 1 in 6 failed.
Google-hosted mail accepts made-up addresses 10 times as often
A catch-all domain accepts mail for any address, so a standard mailbox check cannot tell a real person from a typo. To find them, Verifox offers the domain’s server a randomly generated address that cannot exist. 21.2% of addresses on uploaded lists sat on domains that accepted it.
Where the mail is hosted made a large difference. On uploaded lists, 23.3% of Google-hosted addresses were catch-all, against 2.3% of Microsoft-hosted ones. Among business addresses checked one at a time it was 28.5% against 1.3%. Google Workspace lets administrators route mail for unknown recipients to another mailbox, while Microsoft 365 rejects unknown recipients by default, which fits the gap. For senders it means that a large share of Google Workspace contacts cannot be confirmed by a basic check.
Verifox does not return “unknown” for these addresses. It scores each one from 0 to 100, and for Google and Microsoft addresses it runs a second check that can confirm the mailbox. Of 7,545 catch-all addresses checked one at a time, none came back unknown and 65.2% scored 70 or higher. You can try it on any address with the catch-all email checker.
Disposable addresses were the smallest problem
Disposable addresses, the throwaway inboxes that verification is often bought to stop, were 0.5% of addresses on uploaded lists and 0.1% of single checks. Dead mailboxes were a far bigger problem. Role addresses such as info@ and sales@ were 6.9% and 9.9%. Domains with no mail server at all were 1.4% of single checks, and mistyped domains such as gmial.com were 0.1%.
What this means for your bounce rate
Mailbox providers start throttling senders at a bounce rate of roughly 2%. A list where nearly a third of addresses are undeliverable would blow past that in a single send. The fix is to verify before you send, not after the bounces arrive:
- Clean whole lists with the bulk email checker before every campaign.
- Stop bad addresses at signup with the email verification API.
- Re-verify any list you have not mailed in a few months.
Methodology
The data covers two groups of addresses checked by Verifox customers in 2026. Lists uploaded for cleaning are 272,780 addresses from 157 accounts that uploaded files between October 12 and November 8. Single checks are 188,677 addresses from 256 accounts checked one at a time between July 18 and November 10. Verifox’s own team accounts and accounts banned for abuse are excluded.
Each account counts for at most 5,000 addresses, so one large customer cannot drive a result. Every figure rests on at least 84 accounts, and no account makes up more than 18% of any figure.
Verdicts are Verifox’s standard ones. Undeliverable means the domain has no mail server or the server rejected the mailbox as missing or disabled. Risky means the server accepts mail but the mailbox could not be confirmed. Unknown means the server gave no usable answer. Safe means the mailbox was confirmed. Mail hosts come from each domain’s MX records. A catch-all address that the second check confirmed as a real mailbox counts as safe, so the catch-all figures are a floor.
These are lists people chose to verify, often because they suspected a problem, so they are not a random sample of all email addresses. Only aggregate counts left the database. No address, domain or customer is identified here.
Download and cite the data
Every figure on this page is in the CSV, with the number of addresses and accounts behind it. The data is free to use under CC BY 4.0. Please cite “Verifox Email List Health Report 2026” and link to this page.
Explore more from Verifox
The terms behind these numbers, explained in the Verifox glossary.
Common questions
Email list health, answered
The questions this data answers most often, with the numbers behind each answer.
What percentage of email addresses are invalid?
In Verifox’s 2026 data, 31.9% of addresses on lists uploaded for cleaning were undeliverable, meaning the mailbox or the domain does not exist or the account is disabled. For addresses checked one at a time, such as signups and single lookups, the figure was 19.3%. These are lists people chose to verify, so treat them as a picture of lists before cleaning, not of every address in use.
How many emails on a list will bounce if I don’t verify it?
On the lists in this study, nearly 1 in 3 addresses would have hard-bounced, and a further quarter were risky, mostly catch-all addresses that may or may not bounce. Mailbox providers start throttling senders at around a 2% bounce rate, so an unverified list like these can damage a domain in one send. Running it through a bulk email checker first removes the undeliverable share before it costs you.
Are business email addresses cleaner than Gmail addresses?
Yes, by about half. Among addresses checked one at a time, 15.7% of addresses on business domains were undeliverable, against 33.8% of free-mail addresses such as Gmail, Yahoo and Outlook.com. Business addresses are still far from clean: roughly 1 in 6 failed.
What is a catch-all email address, and is it safe to send to?
A catch-all domain accepts mail for any address, real or not, so a standard check cannot tell whether one mailbox exists. 21.2% of addresses on uploaded lists sat on catch-all domains. Some are real inboxes and some bounce later. Verifox scores every catch-all address from 0 to 100 instead of returning “unknown”: none of the 7,545 catch-alls in the single-check data came back unknown, and 65.2% scored 70 or higher. Send to the high scorers and hold back the low ones.
Why do Google-hosted domains accept every address so often?
We measure what the server does, not why. 23.3% of Google-hosted addresses on uploaded lists, and 28.5% of Google-hosted business addresses checked one at a time, sat behind a server that accepted a made-up address. On Microsoft-hosted mail it was 2.3% and 1.3%. Google Workspace lets administrators route mail for unknown recipients to another mailbox, while Microsoft 365 rejects unknown recipients by default, which fits the gap.
How often should you clean an email list?
Verify any list before you send to it, and re-verify a list you have not mailed in a few months. Addresses go bad as people change jobs and companies shut down mailboxes, and a list that was clean when you built it will not stay clean. The Verifox email verifier checks a whole list in one upload.