When an SMF member deletes their account and then contacts you to delete their posts it’s not an easy request because the posts are no longer attached to a user account. What can you do? You can query the database
Or as I like to call it, “Query to assign guest posts to user who threw a tantrum and deleted their account and then wanted it back again.” We get these at least twice a year, usually around the holidays.
A useful MySQL query to delete a spam PM content on Simple Machines Forum.