Is there a technical interface (API) to *automatically* (i.e., by machine) transmit letters for printing and sending?

At the moment, following sending options are possible:

• Printer driver (suitable for daily mail and small mailings)
• Doc2Print; online solution (suitable for larger mailings, e.g., 5,000 invoices)
• SFTP interface (for business customers with more than 25,000 items per year)

An API interface is already existing, but only for digitally delivered items; to allowed delivery of physical items through this interface, we will adapt it (see also https://api.klara.ch/docs#/).