Why don’t you want to install a Spam Blocker?

How are you going to determine what is Spam without opening it in some way ? Depending on the volume of spam you get this will be time consuming.

You can add rules to your email program to filter spam. It is no use blocking individual email addresses as this is trying to shoot a moving target, many from addresses are forged, you are unlikely to get spam from the same email address to warrant the rule/blocking. There is an overhead as each email is by each email rule/blocking, so it could possibly slow email processing.

I use MailWasher Pro which deletes spam at the mail server, it doesn’t get downloaded (partial info about the email is checked locally) to your inbox fully and then get checked by your rules or other spam killer program (if you had one). There is a free version of MailWasher but that only checks one email account, so if you only have one account no problem.