Ask Leo! #710 – Why Doesn’t Blocking Email Senders Work?

This Week

Featured: Blocking email senders? Don't bother, you're wasting your time.

Also this week: How email gets from point A to point B (hint: relay servers), and that perennial question powering down at night or not?

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Why Doesn't Blocking Email Senders Work?


How can I block addresses that come repeatedly to my junk email box? It says I am blocking email but it does not work.

Blocking email by the “From:” address is seriously overrated; it's effectively useless.

It promises to prevent email from a specific sender from reaching you, but if the sender determined, the block is easily bypassed. And spammers are determined … boy, are they determined! Blocking senders is useless in the war against spam.

I'll explain why, and what I do instead.

Blocking email versus the spam folder

You said the email is coming “repeatedly to my junk email box”. That may be exactly what “blocking email” means to your email program: “When email from this sender arrives, put it in the junk folder.”

That's one definition of what it means to block email.

If that's the way your email program works, it's working exactly as it should.

Misleading email addresses

Spammers work hard to mislead you. One technique makes emails appears as if they're from someone that they're not.

Email addresses have two parts: the email address itself, and an optional “display name”. For example, you might see:

From: Leo A. Notenboom 

The display name is “Leo A. Notenboom” and the email address is

The display name is optional. If it's present, many email programs will display it rather than the actual email address. Your email program might show something like:

From: Leo A. Notenboom

Spammers use this to mislead you. For example:


Here the display name is “”, but the email address is “”. So, in some email programs, you would see this:


It looks like email from, but it's not — it's really from

You can block “” if you like, but it won't block this particular email because that's not where it came from.

Ever-changing email addresses

There's another technique spammers use that renders individual address blocking completely ineffective.

They don't send email 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 different email address. You can block that address if you like, but that won't stop the next email they send, or the one after that, or the one after that … because they all come from different email addresses.

Combined with the tricks spammers use to mislead you about what email address is really being used, things get very confusing very fast.

The short answer is that using sender blocking to stop spam is a waste of time and effort.

Don't bother.


Mark it as spam or junk (depending on the term your email program uses).

Most email programs and services allow you to mark email messages as spam. Do that instead.

Not only will it move the message from your inbox to the junk folder, it also 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 use your Delete key. It's simple, quick, and 100% accurate.

Showing up in the spam folder is the right thing

Email arriving in your spam folder is exactly what should happen if that email is spam. Yes, there might be a lot (I get hundreds a day), but that's the system working exactly as it should.

Trying to prevent the email from reaching you at all — meaning that it never shows up in your email account's inbox, spam folder, or any other folder ever — is pointless. Spam exists, and currently there's no way to stop it.1

The best you and your email service can do is deal with it after it arrives.

For your email service, that means analyzing and sending spam to your spam folder. For you, that means marking spam as spam when it shows up in your inbox, and occasionally marking legitimate email that shows up in your spam folder as “not spam”.

Is blocking good for anything?


Blocking email is good for anything that isn't spam.

For example, if there's a specific individual you 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.

Related Links & Comments: Why Doesn't Blocking Email Senders Work?

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What's a Relay Server?

I ran into a situation the other day where a friend's email address was hijacked and used for sending spam. He was getting numerous bounce-back notices from mail he had not sent. Then his ability to send mail shut down. When we contacted the mail host, we were told that his account had exceeded the relay quota for the day and further that it couldn't be reset manually but would reset naturally over the next day. What is a relay server and how is it different from the regular email server I use at my (different from my friend's) host?

Generally, relaying has a very specific definition, but I'm not certain it applies in your case. Your email provider might be using it in a non-standard way.

Either way, relaying is a fundamental way that email travels from your outbox to your recipient's inbox.

Continue Reading: What's a Relay Server?

Should I Turn My Computer Off at Night?

A friend of mine told me it is better to not turn off my desktop computer every night, instead to turn it off every few nights and just put it on standby every night. I work from home and I use my computer every day. Is it really better to not turn it off every night? I have a four-year-old dell Desktop with one of those old clunky monitors. Is putting it on standby saving as much power as turning it off? Also, does turning the computer on and off affect it negatively?

The issue isn't as simple as you might think; there's no single answer to this perennial question.

My answer, naturally, is “It depends.”

There are two issues at play here: the power used by a computer left running 24 hours a day, and the stress on hardware components being repeatedly turned off and on.

Continue Reading: Should I Turn My Computer Off at Night?

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Posted: June 26, 2018 in: 2018
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