All integrations

n8n

Available

Two nodes: an action node for sending, reading, cancelling, downloading, validating and pricing, and a trigger node that waits for status changes.

What you can do with it

Run a monthly dunning round over overdue invoices from your own database.
Post the PDF from a previous node straight through the binary field.
Have the trigger write the delivery date back into your records.

Connecting it

Install n8n-nodes-sendletter under Settings, Community Nodes.
Create a SendLetter credential with an API key from your account.
Start with a key beginning sk_test_: it runs the whole chain, trigger included, without printing or charging.

The trigger needs an https address, so a local installation needs a tunnel.