Terms of Service

EFFECTIVE DATE: FEBRUARY 11, 2026 · LAST UPDATED: MARCH 2, 2026
Plain language summary: Xail is a lightweight email client that adds split-channel security to your existing email accounts. You keep your email accounts. You own your data. We can't read your messages. These terms govern your use of the Service.

1. Agreement to Terms

By installing, accessing, or using Xail (the "Service"), you agree to be bound by these Terms of Service ("Terms"). If you do not agree, do not use the Service. These Terms constitute a legally binding agreement between you and Xail ("we," "us," or "our").

If you are using the Service on behalf of an organization, you represent that you have authority to bind that organization to these Terms, and "you" refers to that organization.

2. Description of the Service

Xail is a lightweight email client that connects to your existing email accounts (Gmail, Outlook, Yahoo, and other providers) via OAuth 2.0. Xail provides:

Important: Xail is not a replacement for Gmail, Outlook, or any other email service. Xail is a client that connects to your existing email accounts. You retain full access to your email through your provider's own interface at all times.

3. Eligibility

You must be at least 13 years old (or the minimum age in your jurisdiction) to use Xail. If you are under 18, you must have your parent's or guardian's consent. By using Xail, you represent that you meet these requirements.

4. Account and Security

4.1 Email Account Connection

Xail requires you to connect at least one email account via OAuth 2.0. You are responsible for maintaining the security of your email accounts. Xail does not store your email passwords — authentication is handled entirely by your email provider.

4.2 Split-Channel Security

Xail's split-channel security depends on you maintaining separate, independent email accounts with different email providers. The security guarantees of Xail's threshold sharing system are based on the assumption that these accounts are not controlled by the same party (other than you). Using multiple accounts at the same provider (e.g., two Gmail accounts) reduces the independence guarantee.

4.3 Your Responsibility

You are responsible for all activity that occurs through your connected email accounts within Xail, keeping your devices and email accounts secure, ensuring your connected email accounts remain active and accessible, and understanding that disconnecting email accounts may affect your ability to reconstruct previously received secure messages.

5. Service Tiers and Pricing

Current status: Xail is in early access. During this period, all features are available at no cost. Paid tiers and pricing will be announced in the future. We will provide at least 30 days' notice before any paid features are activated.

5.1 Security Tiers

Xail's security level depends on the number of independent email addresses you connect:

TierAddressesSecurity Level
Gray1Unsecured — regular email only, no security tier
Blue2Secured — 2-of-2 threshold, no single provider can read your messages
Green3Secured + fault tolerant — 2-of-3 threshold, messages survive one provider outage

5.2 User Accounts and Cross-Device Sync

Your first connected email address serves as your Xail identity. Your account data — including connected account metadata, settings, contacts, and preferences — is synced across devices so that connecting the same email on a new device restores your profile. Only metadata is synced. Message content, shares, and plaintext are never stored on or transmitted through Xail servers.

5.3 Enterprise Agreements

Enterprise usage is governed by a separate Enterprise Agreement that supplements these Terms. Enterprise Agreements may include custom terms for compliance, SLA, data handling, and support. In the event of a conflict between these Terms and an Enterprise Agreement, the Enterprise Agreement controls.

6. Acceptable Use

You agree not to:

We reserve the right to suspend or terminate accounts that violate these terms.

7. Intellectual Property

7.1 Xail's Intellectual Property

The Service, including its design, interface, code, and documentation, is owned by Xail and protected by intellectual property laws. The split-channel secure messaging method is the subject of a pending patent application. The Xail name, logo, and brand elements are trademarks of Xail.

7.2 Open-Source Components

Xail's cryptographic library implements the XorIDA threshold sharing algorithm over GF(2). The cryptographic implementation is tested with known-answer test vectors and 100% line coverage. When published, open-source components will be provided under their respective licenses.

7.3 Your Content

You retain all rights to your email content. Xail does not claim ownership of any messages, attachments, or data you create, send, or receive through the Service. Because Xail processes content only on your device, we never have access to your content on our servers.

8. Privacy

Your use of the Service is also governed by our Privacy Policy, which is incorporated into these Terms by reference. The Privacy Policy describes our zero-knowledge architecture and explains how your data is handled.

9. No Guarantee of Delivery

Xail relies on third-party email providers (Gmail, Outlook, Yahoo, etc.) to deliver messages. We do not guarantee message delivery, delivery timing, or delivery order. Delivery depends on the uptime and performance of your email providers, your internet connectivity, and the recipient having an active Xail installation with sufficient shares available for reconstruction.

For secure messages using a 2-of-3 threshold (Green tier), the message can be reconstructed even if one email provider experiences downtime.

Deferred delivery: When you send a secure message to a recipient who does not yet use Xail, one share is delivered to their existing email with an invitation to join. The remaining share is held on your device indefinitely until the recipient joins Xail. There is no expiry on held shares — they remain available for delivery as long as your Xail client retains them.

10. Disclaimers

THE SERVICE IS PROVIDED "AS IS" AND "AS AVAILABLE" WITHOUT WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT.

While Xail's split-channel architecture provides information-theoretic security guarantees based on the independence of your email providers, we do not warrant that the Service will be uninterrupted, error-free, or completely secure against all forms of attack. No security system is perfect.

Xail is not a law firm, medical practice, or financial institution. The Service provides tools that may help with regulatory compliance (HIPAA, attorney-client privilege, financial data protection), but using Xail alone does not make you compliant with any specific regulation. You are responsible for your own compliance obligations.

11. Limitation of Liability

TO THE MAXIMUM EXTENT PERMITTED BY LAW, XAIL SHALL NOT BE LIABLE FOR ANY INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL, OR PUNITIVE DAMAGES, OR ANY LOSS OF PROFITS OR REVENUES, WHETHER INCURRED DIRECTLY OR INDIRECTLY, OR ANY LOSS OF DATA, USE, GOODWILL, OR OTHER INTANGIBLE LOSSES RESULTING FROM:

IN NO EVENT SHALL XAIL'S TOTAL LIABILITY EXCEED THE GREATER OF (A) THE AMOUNT YOU PAID TO XAIL IN THE TWELVE MONTHS PRECEDING THE CLAIM, OR (B) ONE HUNDRED DOLLARS ($100).

12. Indemnification

You agree to indemnify, defend, and hold harmless Xail and its officers, directors, employees, and agents from any claims, liabilities, damages, losses, and expenses (including reasonable attorneys' fees) arising from your use of the Service, your violation of these Terms, or your violation of any applicable law or the rights of any third party.

13. Modifications to the Service

We reserve the right to modify, suspend, or discontinue any part of the Service at any time. We will provide reasonable notice for material changes. If we discontinue the Service entirely, we will provide at least 90 days' notice and guidance for exporting your local data.

14. Modifications to These Terms

We may update these Terms from time to time. Material changes will be communicated through in-app notification and by updating the "Last Updated" date. Your continued use of the Service after changes are posted constitutes acceptance. If you disagree with changes, your remedy is to stop using the Service.

15. Termination

You may stop using Xail and disconnect your accounts at any time. We may terminate or suspend your access if you violate these Terms. Upon termination, your right to use the Service ceases immediately. Provisions that by their nature should survive termination (including Sections 7, 10, 11, 12, and 17) will survive.

16. Third-Party Services

Xail integrates with third-party services through their APIs:

Xail is not responsible for the practices, availability, or data handling of third-party services. By using AI assistant features, you acknowledge that your interactions are also subject to the respective provider's terms and policies.

17. Governing Law and Disputes

These Terms are governed by the laws of the State of California, United States, without regard to conflict of law principles. Any disputes arising from these Terms or the Service shall be resolved in the state or federal courts located in Los Angeles County, California. You consent to the personal jurisdiction of these courts.

For Enterprise customers, alternative dispute resolution mechanisms may be specified in the Enterprise Agreement.

18. General Provisions

19. Contact

For questions about these Terms, contact us at:

Xail
Email: contact@xail.io
Web: https://xail.io
Los Angeles, California, United States

These Terms of Service were last reviewed on March 2, 2026.

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