Read this order
Rider → Letter: News arriving in writing: a message, email, notice or document that brings a new development.
What changes in reverse?
Letter → Rider: A document or written message being delivered or passed on. The emphasis is on the movement of information.
Letter → Rider ↗A practical example
Consider an application awaiting a reply. Rider + Letter can fit news arriving as an email. Letter + Rider begins with the email and emphasizes its delivery or forwarding. Check the actual message rather than inferring its contents from the cards.
Check it against your question
Keep the actual order and ask which part of the example fits your situation. An example illustrates a possible reading; it does not establish facts or promise an outcome.
Compare two real-life contexts
For a job application, Rider + Letter can suggest incoming written news; for an event, it can suggest an invitation arriving. Letter + Rider starts with the document and emphasizes delivery or forwarding. Neither order tells you whether the application succeeded or whether the invitation is welcome. If Mountain follows, consider delay; if Book follows, consider information not yet understood. Verify the actual message before interpreting its contents.
The meanings behind the pair
Rider: The Rider brings news, a visitor or a new arrival. It usually adds movement and a relatively quick pace.
Letter: Letter is a written message, document, notice or record. It draws attention to the information itself and to how it has been communicated.
These examples show possible ways to read the pair. Your question and the other cards may change the meaning.