Terms of Service

Last updated October 12, 2026

The service

Plumbline provides automated checks of email addresses and phone numbers through an API and an MCP server. Results are best-effort signals based on public DNS data and phone numbering metadata. They are not a guarantee that a message will be delivered or that a number is in service.

Credits and payment

Credits are prepaid through Stripe, never expire, and are consumed at one credit per check. The free allowance (50 checks per day per client) may change or be limited to prevent abuse. If credits were bought by mistake and not used, email us within 30 days for a refund.

Acceptable use

Don't use Plumbline to validate lists for unsolicited bulk messaging that breaks anti-spam laws, to harass anyone, or to overload the service. We may suspend keys that do.

API keys

Keep your key private. Anyone with the key can spend its credits.

Liability

The service is provided as is. To the extent allowed by law, our liability is limited to the amount you paid for credits in the previous three months.

Contact

Plumbline is operated by SilverQueen EOOD, 156 Cherni Vrah Blvd, 1000 Sofia, Bulgaria. Email sawhorsesites@gmail.com.