In Outlook IMAP search command, the supported search operators are limited compared to some other email providers like Gmail. The operators you mentioned, such as "SINCE," "SUBJECT," "OR," and "NOT," are indeed supported by Outlook IMAP search.
However, the "KEYWORD" operator you tried is not supported in Outlook IMAP search. Outlook doesn't have a direct equivalent to Gmail's "X-GM-RAW" extension, which allows you to use raw search queries directly in Gmail IMAP.
In Outlook, the available search operators are generally standard IMAP search operators, and the functionality might not be as advanced or flexible as what you can achieve with Gmail's "X-GM-RAW" extension.
If you need more advanced search capabilities in Outlook, you might consider using the Outlook API or Microsoft Graph API, which provide more extensive search functionalities. Keep in mind that using APIs might require additional programming or development work compared to directly using IMAP commands.
Let me know if you have any other questions or if there's anything else I can help you with!