Postmark ✰ ❲Plus❳

For businesses sending invoices, legal notices, or certified documents, the postmark serves as a receipt of dispatch. The USPS offers "Postmarked Proof of Mailing" services, but even a standard postmark can hold up in small claims court as evidence that a letter was sent on a specific day.

The API doesn't stop at sending. It offers powerful features including:

To send the email, you pass a JSON "TemplateModel" through the Postmark API

Ironically, as we rely on email, the physical postmark has become more valuable specifically because it is physical. Email headers can be spoofed; "Sent" times can be manipulated by changing a device's clock. But a physical ink postmark is incredibly difficult to fake without access to heavy-duty industrial printing equipment.