Sometimes emails are mistakenly marked as spam or put into Trash, and they can be difficult to discover via search. To help address this issue, Gmail will now search in both the Trash and Spam folders (only Trash was indexed previously). If a match is found, a footer at the bottom of search results will indicate the match and direct the user to view the messages.
In addition, if a search query is too general to return useful search results, a different footer will now be shown guiding the user to try refining their query using Gmail advanced search.
This update will take effect in early December.