Yahoo Mail has a Spam folder. Yahoo will move suspected spam into this folder. You can set how long it will remain in the folder before it is emptied. If you do receive spam in your inbox you can set a filter so that it won't go into your inbox in the future. This must be done on the Yahoo web site and not in Apple's Mail app. The Spam folder on Yahoo is the Bulk folder in the Mail app.
"SpamGuard is ON:[Edit Settings]
SpamGuard ensures that suspected spam is delivered to the Spam folder, and is deleted after one week.What's this?"******