Within Mac mail you can mark items as Junk, but if using another ISP like yahoo with mac mail, these Junk emails are not relayed to the ISP, so it only helps if you use Mac mail forever. https://c-command.com/spamsieve/ is a good solution as well with a free trial so you can see if it works for you. Whether Mac mail or another antispam program the key is to train it by marking what you see as spam so it can do its job the best.