depending on your isp, you may well have web mail access, for example talktalk or tiscali( now talktalk) email addresses all have a web mail box where you can log in from any pc, anywhere and check you emails without the need to download them to your pc.
On web mail there may well be a settings menu, and in this you can set up various filters, even selecting various email address that can be blocked. Filters can be set up that look for certain words or phrases and block those addresses. It takes a while but i spent time selecting emails that were to be added to the blocked senders list.
I use this service as it means the spam is blocked on the webmail server and not your pc.
If you block it on your pc then your pc still downloads/ or checks the web server before blocking, rejecting , deleting it. If you get lots of emails this can take quite a while.
Also always make sure that you tick or untick " email" boxes on websites you may register on. Read the small print carefully, as some sites will say " tick the box if you DONT ...." and others " Untick the box" etc
Where you get emails that ask you to unscribe from receiving emails , dont follow the link unless its a known site you registered with as, once be you have confirmed the email address is valid they will sell it on. Just add it to your blocked senders list.
I have 3 email addresses and recieve very little spam these days. My webmail does have a trash box full of rubbish that is deleted automatically every 2 to 3 days by the email server.