If you have a cloud-hosted LiveAgent account and you are using the built-in email directly, or you are forwarding emails to the built-in email account, all received emails are automatically checked by the SpamAssassin service installed on our cloud servers. If the email is recognized as spam, it will also be fetched with the Spam status into your LiveAgent account.
If you are fetching emails to your LiveAgent account from your mail server via Google/Microsoft connectors or IMAP/POP3 methods, it's the responsibility of your mail server to have some spam filter that will mark an email as spam when it's received (add email header X-Spam-Status). When LiveAgent fetches new emails from your mail server, it can already see what is marked as spam and set the appropriate status to a ticket.