Blocking email contact doesn't work

Unfortunately, as you've discovered, blocking a specific email address does not work to prevent spam and junk from showing up in your email box. The bad actors are always just a single alphanumeric from recurrence and this makes that strategy useless.

Some here in the Community will suggest the use of a filter such as SpamSieve from c-Command Software as a workable solution. There are others.

Others will suggest that you train the filters already built into the Mail app: Reduce junk mail in Mail on Mac - Apple Support. This works fairly well for me. I still get my share of junk, but it gets dropped into the Junk mailbox where I can quickly scan it, look for anything I might not wish to delete (new correspondence from non-contacts) and then delete the rest (option-command-j).

Somehow, somewhere your email address has fallen into the hands of some entity that has likely sold it off as part of some email address list. There's no telling what company/entity did that. It seems to happen to us all.

All junk mail is suspicious. If you didn't directly solicit the contact, then treat it all as potential trouble.

Please see:

Effective Defenses Against Malware - Apple Community

and

Avoid phishing emails, fake 'virus' alerts…and other scams - Apple Support