Terms of Service

The terms under which DUST 4 Business, s.r.o. operates postfly: invite-only access, acceptable use, limits, liability and governing law.

Effective from: 15 September 2026

1. Operator

postfly is operated by DUST 4 Business, s.r.o., Bratislavská 31, 010 01 Žilina, Slovakia, company ID (IČO) 50394177, tax ID (DIČ) 2120308971. Registered in the Commercial Register of the District Court Žilina, Section: Sro, File No. 65980/L. ("Operator", "we", "us").

2. Definitions

• Service — the postfly transactional email platform: the dashboard, the /v1 API and the SMTP relay described in the Quick start.
• Customer — the business or entrepreneur whose account sends mail through the Service.
• Account — the sign-in identity created for a Customer's team member by invitation.
• Recipient — a person or organization to whom a Customer sends a message through the Service.
• Content — the messages, attachments and recipient data a Customer sends or stores through the Service.

3. Access and accounts

Access to postfly is by invitation only. An Account is created when someone accepts an invitation sent by the Operator or by an existing Customer's team; it is bound to the email address the invitation was sent to. There is no public sign-up. The Operator may decline to issue or may revoke an invitation at its discretion.

The Customer is responsible for the accuracy of the information it provides, for keeping API keys and account credentials confidential, and for all use of the Service made under its Accounts and API keys, including by its own employees and contractors.

4. Price

The Service is currently provided free of charge. The Operator may introduce charges in the future, but only after giving Customers advance notice. A Customer that does not wish to accept the new terms may stop using the Service and withdraw before the charges take effect, with no obligation to pay them.

5. Acceptable use

The Customer must not use the Service to send, or to help anyone else send:

• unsolicited or bulk marketing messages sent without the recipient's consent;
• mail to purchased, rented or otherwise non-consensually obtained recipient lists;
• phishing or other messages that impersonate a person or organization;
• malware, or messages that link to or carry malware;
• content that is illegal under the law applicable to the sender or the recipient.

The Operator enforces sender-domain authentication, sending limits and suppression lists described in the Concepts and the Deliverability; a Customer's mail is measured against these automatically.

6. Limits

Sending is subject to technical limits enforced by the Service and documented in the Warmup & daily caps and Daily sending quota — including sender-domain verification, a warm-up period for new domains, a daily sending cap, and limits on attachment count, size and file type. This page does not restate those numbers so it cannot drift from what the Service actually enforces; the current values are always current at those links.

7. Suspension and termination

The Operator may suspend or terminate an Account's or a Customer's access, in whole or in part, where it reasonably believes the Service is being used in breach of Section 5 (Acceptable use), to protect the Service, other Customers or third parties, or to comply with the law. Where practical, the Operator gives notice of the reason.

Either party may stop using, or terminate access to, the Service at any time. On termination, Content is retained and then erased on the schedule set out in the Privacy Policy.

8. No availability guarantee

The Service is provided on a best-effort basis. The Operator gives no service-level guarantee and no uptime commitment; maintenance, incidents or third-party outages (see Data Processing Agreement) can interrupt it.

9. Liability

The Service is provided "as is", free of charge, with no guarantee of availability, delivery, inbox placement or timeliness, and no SLA — see Section 8 above.

The Operator is not liable for lost profit, indirect or consequential damage, or loss of data. postfly is not an archive: message content (subject, body, headers) is erased 30 days after a message reaches its final delivery status, and the message record itself at the latest 90 days after — see Privacy Policy. The Customer is responsible for keeping its own copies of any message or record it needs to retain.

The Operator is not liable for damage caused by the Customer's own Content, by a Recipient's mail server, by a blocklist decision, or by an outage of a third party listed in the Data Processing Agreement.

None of the exclusions in this Section apply where the law forbids them, in particular for damage caused intentionally (úmysel) or by gross negligence (hrubá nedbanlivosť).

10. Personal data

How the Operator processes personal data as controller of its own Customers' account data, and as processor of the data Customers send through the Service, is set out in the Privacy Policy and, for the processing carried out on a Customer's instructions, in the Data Processing Agreement.

11. Changes to these Terms

The Operator may change these Terms. A material change is announced to Customers with advance notice before it takes effect. Continuing to use the Service after a change takes effect means the Customer accepts the updated Terms; a Customer that does not accept a change may stop using the Service beforehand.

12. Governing law and disputes

These Terms are governed by the law of the Slovak Republic, without regard to its conflict-of-laws rules.

For business relations (B2B), the parties agree that disputes are decided by the Slovak court with subject-matter and territorial jurisdiction according to the Operator's registered seat in Žilina.

13. Effective date

These Terms take effect on 15 September 2026.