If you've blocked it yourself it isn't junk mail as such although the above advice will solve your real junk mail problem.
A better thing to do for you I think rather than block is to set up a 'rule' for each address you want to get rid of.
This you can find in 'preferences> rules tab'.
You would choose 'from' in the first line then add 'is' the address then paste the address
in the next 'action' line you choose 'delete'. Then they go as they arrive and you never see them.
It is often useful to choose a part of the address as you might get messages from
no-reply@123shop.com or
sales@123shop.org so you would just use 'from' then 'contains' 123shop and it'll get all of them.
Rules are powerful and really useful so if you are getting messages saying '50% off!! you can set up a rule to delete anything which says 50% off. O 'newsletter'. I have one that deletes any message ending in two '!! 'for instance. And so on....
It's trickier if you are getting junk mail defined by the ISP and it's putting it in their own box. I have one called 'Quarantine' provided by my ISP and junk filtering and rules can't do anything to it.
There is a solution but it's more difficult to explain.
You have to go into preferences>account' your email >mail box settings and choose that box (Quarantine in my case) as the junk mail box. Then it will put all junk mail into that box, Apple and including the ones from your ISP and it won't notify when they arrive.
In the mail box settings you can choose when to delete them- one day, a month or on exit. You can't delete them instantly but you won't get notified.
It can be useful to do this if you are also getting false positives. Just check every so often.
