Below is a based on a generic understanding of such a book.
Let me check if there's any common usage of "Rasail O Masail" in specific contexts. A quick search shows it's commonly used in Islamic jurisprudence as a format for categorizing legal rulings (Rasail) and their corresponding questions or cases (Masail). So maybe the user is referring to a document structured similarly in a religious context. But without more info, it's safer to assume a general context. Rasail O Masail.pdf