How can I use Advanced Query Syntax (AQS) to search for emails within a specific date range using exchangelib?

Exchangelib supports AQS via the `querystring` parameter. For a date search, you can use syntax like `sent:>=2021/1/1 AND sent:<=2021/12/30` or `received:>=2021/1/1 AND received:<=2021/12/30`. However, note that AQS cannot be used for keyword searches directly; you must first retrieve emails and then perform string matching in Python. The open‑source downloader demonstrates this by implementing an AQS‑based search feature alongside folder enumeration and attachment extraction.