I am always amazed at the number of junk emails that are in my spam folder. Most email providers do a pretty good job of sorting out the good from the bad, but not always.
The best way to make sure you get the emails you want is to add them to your contact list so your provider will know you want them, and they will go directly to your inbox.
Having a junk mail filter is a big time saver. Even if you don't read them and just go through and delete them, this takes up time and gets to be annoying.