The short version
- isBusinessEmail is free. In return, please use it fairly and within the limits.
- Verdicts are probabilistic. We don’t guarantee accuracy or uptime. Keep a fallback.
- Don’t resell the API, scrape our data, use it for spam or list-washing, or dodge the limits.
- Your API keys are your responsibility.
- We can suspend accounts that break these terms.
- Material changes come with 30 days’ notice. Lithuanian law applies.
The full terms below are what count. Where this summary and the full terms differ, the full terms apply.
1. Who we are
isBusinessEmail (“the Service”, “we”, “us”) is operated by Tilfortis MB, a small partnership (mažoji bendrija) registered in Lithuania. Contact: hello@isbusinessemail.com.
2. Accepting these terms
2.1. By creating an account, creating an API key or using the API, you accept these Terms and our Acceptable Use Policy, which forms part of them. Our Privacy Policy explains how we handle personal data.
2.2. If you use the Service for an organization, you confirm that you’re authorized to accept these Terms for it, and “you” includes that organization.
2.3. You must be at least 16 years old to create an account.
2.4. The public checker on our website can be used without an account. These Terms apply to that use too, except the sections that only make sense for accounts.
3. The Service
3.1. The Service classifies email addresses and domains: for example whether an address is on a custom (business) domain or a shared-domain provider, whether it’s disposable, a relay or on a blocklist, and whether the domain’s organization uses Google Workspace or Microsoft 365. It returns a category, a recommendation and the reasons for them.
3.2. Verdicts are informational and probabilistic. They’re based on lists, public DNS and other public signals, which can be incomplete, outdated or wrong. You decide what to do with a verdict, and you’re responsible for the decisions you make about your users. Design your systems so that an incorrect verdict, a timeout or an outage doesn’t cause harm. In particular, provide a way for people to reach you if a check blocks them.
3.3. The Service doesn’t verify whether individual mailboxes exist and doesn’t identify individuals.
3.4. We may change, add or remove features. For API changes we follow our versioning and deprecation policy.
4. Free service and fair use
4.1. The Service is provided free of charge.
4.2. Use is subject to limits (for example requests per second, checks per day, batch sizes) published in our documentation or shown in your dashboard. We may change the limits at any time, for everyone or for particular accounts, to protect the Service. We may raise limits on request at our discretion.
4.3. There’s no service level agreement. We aim for high availability but don’t promise it.
5. Accounts and API keys
5.1. Keep your account details accurate. You can sign in with Google, Microsoft or an email link.
5.2. API keys are your responsibility. Keep secret keys secret, don’t embed them in client-side code, and revoke keys you suspect are exposed. You’re responsible for all use of your keys until you revoke them.
5.3. We may revoke a key that we believe is exposed (for example, one reported to us by GitHub secret scanning) and we’ll tell you when we do.
5.4. One person or organization, one account, unless we agree otherwise. Don’t create additional accounts to get around limits or suspensions.
6. Prohibited use
You must not, and must not help anyone else to:
- resell, sublicense, rent or wrap the API (or its output) as a paid or free product or service whose main value is our data or verdicts, without our written permission;
- scrape, sweep or bulk-harvest our data, lists or verdicts, including systematically checking domains or addresses to rebuild our dataset;
- use the Service for spam, list-washing or cleaning lists of addresses you don’t have a lawful basis to email;
- get around limits or protections, including rotating keys, accounts, IP addresses or networks, automating the public checker, or bypassing robot protection;
- create multiple accounts to evade quotas or suspensions;
- probe, scan or test the Service’s security except as allowed in our security policy;
- interfere with the Service or other users, or overload our infrastructure;
- use the Service unlawfully, including in breach of data protection law, or to discriminate unlawfully against people;
- submit special categories of personal data or anything other than email addresses and domains you’re checking.
The Acceptable Use Policy gives more detail and examples.
7. Your data and your users
7.1. You confirm you have a lawful basis to submit the email addresses and domains you check, and that you’ve informed the people concerned as the law requires.
7.2. Where we process personal data on your behalf to produce verdicts, our Data Processing Agreement applies and forms part of these Terms. The Privacy Policy describes the processing we do as a controller.
7.3. We don’t store full email addresses you check. See Privacy and data.
8. Our rights
8.1. The Service, its software, lists, models, documentation and brand belong to Tilfortis MB or our licensors. We grant you a limited, non-exclusive, non-transferable, revocable right to use the Service under these Terms.
8.2. Lists we publish for download are licensed under the terms stated alongside them. Third-party data we use remains under its original licenses.
8.3. Feedback. If you send us suggestions or verdict corrections, we may use them freely to improve the Service, without obligation to you.
9. Third-party services
The Service relies on third parties (for example Cloudflare, Hetzner, Google, Microsoft and Brevo) and on public infrastructure such as DNS and RDAP. We’re not responsible for their availability or content.
10. No warranty
To the extent permitted by law, the Service is provided “as is” and “as available”, without warranties of any kind, express or implied, including accuracy, completeness, fitness for a particular purpose, availability and non-infringement.
11. Limitation of liability
11.1. To the extent permitted by law, Tilfortis MB is not liable for indirect or consequential losses, lost profits, lost revenue, lost data, lost customers or business interruption, arising from or related to the Service, including decisions you make based on verdicts.
11.2. To the extent permitted by law, our total liability for all claims relating to the Service in any 12-month period is limited to EUR 100, reflecting that the Service is free.
11.3. Nothing in these Terms limits liability that cannot be limited by law, including liability for intentional misconduct or gross negligence, or for death or personal injury caused by negligence.
12. Indemnity
If you use the Service for a business, you’ll defend and indemnify Tilfortis MB against third-party claims arising from your breach of these Terms or your unlawful use of the Service, including your decisions about your users.
13. Suspension and termination
13.1. You can stop using the Service and delete your account at any time from your dashboard.
13.2. We may suspend or restrict your account, keys or access, with or without notice, if we reasonably believe you’ve breached these Terms, your use creates risk for the Service or others, or we’re required to by law. Where reasonable we’ll tell you why and how to appeal.
13.3. We may discontinue the Service. If we do, we’ll give at least 30 days’ notice by email where possible.
13.4. Sections that by their nature should survive termination (including 8, 10, 11, 12 and 15) survive.
14. Changes to these Terms
14.1. We may update these Terms. Each version has a version date at the top, and the changes are listed below.
14.2. For material changes we’ll email account owners at least 30 days before they take effect. You’ll be asked to accept the new version at your next sign-in. During the 30 days your API keys keep working (responses carry a Warning header); after that, the API returns terms_not_accepted until someone on the account accepts.
14.3. Minor changes (clarifications, typos, contact details) take effect when published.
15. Governing law and disputes
15.1. These Terms are governed by the laws of the Republic of Lithuania, excluding its conflict-of-law rules.
15.2. The courts of Vilnius, Lithuania have jurisdiction over disputes, except that if you’re a consumer, you keep any mandatory right to bring proceedings in the courts of your country of residence and any mandatory consumer protections of that country.
15.3. Before going to court, please contact us. Most issues can be solved by email.
16. General
- These Terms, with the Acceptable Use Policy, the Privacy Policy and (where applicable) the DPA, are the whole agreement about the Service.
- If a provision is unenforceable, the rest stays in force.
- Not enforcing a right isn’t a waiver of it.
- You may not transfer your rights under these Terms without our consent; we may transfer ours to a successor of the Service.
- These Terms are written in English. Translations are for convenience; the English version prevails.
Contact
Tilfortis MB, Lithuania · hello@isbusinessemail.com
Changes
| Version | Changes |
|---|---|
| 2026-10-04 | First version. |