Terms and Acceptable Use

Last updated October 17, 2026

These terms apply to anyone using Mailstack, operated by Clutchclick. By using Mailstack you agree to them.

Acceptable use

You may only send email to people who asked to get it from you. In particular, you agree that you will:

• Only email people who opted in to hear from you, and keep a record of how they did.
• Never send to bought, rented, scraped or shared lists, or to addresses harvested from websites.
• Send from a domain you own, with an accurate from name and a subject that isn't misleading.
• Include your postal address and keep the unsubscribe link working, and honor every unsubscribe.
• Follow anti-spam laws where you and your recipients are, including CAN-SPAM, CASL and GDPR.
• Never send phishing, malware, illegal content, or content that harasses or deceives people.

Enforcement

Mailstack suppresses addresses that bounce or complain, and pauses a sender automatically past 2% bounces or 0.08% spam complaints over seven days, and blocks it past 5% or 0.3%. We may also suspend an account that breaks these rules or puts our sending reputation at risk, and may close it without refund for serious or repeated abuse.

Your account and content

You're responsible for your account, your API keys, and what you send. You keep ownership of your content and contacts, and you give us the rights we need to store and send them for you.

The service

Mailstack is provided as is during early access. We work to keep it available and secure, but we don't guarantee that every email is delivered, and we aren't liable for indirect damages or lost profits. Our total liability is limited to what you paid us in the twelve months before a claim.

Open source

Mailstack's software is open source under the GNU Affero General Public License v3.0. These terms cover the hosted service; the license covers the code.

Changes and contact

We'll post changes to these terms here. Questions or abuse reports: hello@mailstack.ai.