If you used a filter such as '@yahoo.com' all email from any user whatsoever using that domain would end up in the junk folder. A specific email would have an effect like that of a kill-filter but usually junk or spam varies the ID source so it wouldn't block it for long.

Hi, thanks for replying. Are you able to send me a link where it would show how to set up that type of filter? I looked at a couple items but was more confused than anything else. Any help would be greatly appreciated. Thanks!!!!

Hamburger (top right)/Tools/Message Filters

Thanks, that is where I have been looking just not sure how to do a server like @yahoo.com or the one I am dealing with a lot right is @live.com. I want to block anything and everything from @live.com. Do I just put in the Filter Name @live.com or do I use something like *@live.com.?

Also how do I fill out the rest of the screen. I tried adding @live.com and so far no luck with blocking sending it to junk mail.

https://support.mozilla.org/en-US/kb/organize-your-messages-using-filters

ok, thank you, I will look it over again