In my opinion, blocking email by sender is seriously overrated.
It promises to prevent a sender’s email from reaching you, but if that sender is determined enough, the block is easily bypassed.
And spammers are determined … boy, are they determined! So much so that blocking senders is pretty much useless in the war against spam.
I’ll explain why, and what I’d do instead.
Blocking email and the spam folder
I want to start by clearing something up.
You said that the mail is coming “repeatedly to my junk email box”. That may be what blocking email means in your email program: “when email from this sender arrives, put it in the junk folder”.
That’s what the junk folder (often also called the “spam” folder) is for, and that’s one definition of blocking email.
Different email programs use different techniques and definitions, but if that’s the way your program works, then it’s working as expected.
Misleading email addresses
Spammers work hard to mislead you. One technique is to make emails look like they’re from someone that they’re not.
Email addresses are typically comprised of two parts: the email address itself, and an optional “display name”. For example, you might see:
From: Leo A. Notenboom <firstname.lastname@example.org>
There you can see both the display name, “Leo A. Notenboom”, and the email address, email@example.com, and it’s pretty obvious which is which.
The display name is optional, but if it’s present, many email programs will display it, and not the actual email address. In that case, your email program might show you something like this:
From: Leo A. Notenboom
Your email program might show you the actual email address if you hover your mouse pointer over the display name, or perhaps click on it.
Spammers, on the other hand, often do this:
From: firstname.lastname@example.org <email@example.com>
Here the display name is “firstname.lastname@example.org”, but the actual email address is “email@example.com”. So in some email programs, you would see this:
It looks like email from firstname.lastname@example.org, but it isn’t.
You can block “email@example.com” if you want, but that won’t block this particular email, because that’s not where it actually came from.
Ever-changing email addresses
Because spammers can manipulate the “From:” address so easily, there’s another technique they use that renders individual address blocking completely ineffective.
They simply don’t send “From:” the same address more than once.
You might get the exact same spam over and over, but each time it’ll be “From:” a completely different address. You can block that address if you like, but that won’t impact the next email they send, or the one after that, or the one after that, because they will come from a different address.
Couple that with the tricks spammers use to mislead you as to exactly what email address is really being used, and things get very confusing very fast.
The short answer is that using sender blocking to stop spam is a waste of time and effort.
Most email programs, and almost all web-based email services, mark emails as spam. This allows the service to learn what is and isn’t spam. While the spam may not get blocked immediately, as you report more and more spam over time, more of it will get blocked: the software will send it to your spam folder instead of your inbox.
Google’s spam filter (as used in Gmail) seems to be particularly effective these days.
If that doesn’t work, I suggest you relax and just use your Delete key. It’s simple, quick, and 100% accurate.
Is blocking good for anything?
Blocking email is good as a start for just about anything that isn’t spam.
For example, if there’s an individual that you specifically want to block, you can block their email address.
But as I mentioned earlier, even then, blocking will be ineffective if they are sufficiently motivated to get through.
All they need to do is get a new email address to send from… and those are trivially easy to get.