Why Doesn’t Blocking Email Senders Work?

Blocking addresses is futile.

Most email programs can block email from a specific address. Unfortunately, that's completely ineffective when it comes to spam.
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Question: 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 useless in the war against spam.

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

I’ll explain why blocking is pointless and what I do instead.

TL;DR:

Blocking is futile

Trying to stop spam by blocking the sender is futile because spammers change who the email appears to be from. The better approach is to mark spam as spam when it appears in your inbox. If it’s showing up in your spam folder, the system is working properly.

Blocking versus the spam folder

You said the email is coming “repeatedly to my junk email box”.

That is the system working exactly as intended: spam should show up in your spam or junk folder rather than in your inbox.

In fact, depending on your email program or interface, that may be exactly what “blocking” means: “When an email from this sender arrives, put it in the junk folder.”

If this is the case, there’s nothing to fix because nothing is broken.

Misleading email addresses

Spammers work hard to mislead you. One technique, “From: spoofing”, makes emails appear as if they’re from someone 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 <leo@somerandomservice.com>

The display name is “Leo A. Notenboom” and the email address is leo@somerandomservice.com.

The display name is optional. When present, many email programs will display it in place of the email address. Your email program might show something like:

From: Leo A. Notenboom

Spammers use this to mislead you. For example:

From: nancy@reallybigbookstore.com <leo@somerandomservice.com>

Here, the display name — not the email address — is “nancy@reallybigbookstore.com”. The actual email address is “leo@somerandomservice.com”. So, in some email programs, you would only see this:

From: nancy@reallybigbookstore.com

It looks like an email from nancy@reallybigbookstore.com, but it’s not — it’s really from leo@somerandomservice.com.

You can block “nancy@reallybigbookstore.com” if you like, but it won’t block this 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 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 it won’t stop the next email they send, or the one after that, or the one after that, because they all come from unique email addresses.

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

The short answer is that using Block the Sender to stop spam is a complete waste of time and effort.

Don’t bother.

Instead…

If the email arrives in your spam/junk folder already, ignore it. The system is working as designed.

If the message arrives in your inbox, mark it as spam or junk.

Marking it as spam will move the message from your inbox to the junk folder, but it also allows the service to learn what is and isn’t spam. 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.

Gmail’s spam filter seems to be particularly effective.

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

I need to reiterate that 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 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?

Yes.

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’re sufficiently motivated to get through. All they need to do is get a new email address to send from, and those are easy to get.

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Footnotes & References

1: In my opinion, so-called “Challenge/response” services are not a viable option.

36 comments on “Why Doesn’t Blocking Email Senders Work?”

  1. This thread has been a revelation to me – thank you.
    Every single day I spend time assiduously unsubscribing, blocking, sweeping, marking as junk etc etc etc in the (apparently vain) hope that these 400 or so unwanted items will stop coming. Seems like my approach has been completely wrong and apparently, in the case of unsubscribing, making things worse.
    It does seem so wrong that I have so little ownership and control over my own email address.
    The trouble is, if I don’t try to deal with the mountains of spam, I lose sight of the genuine and important emails I need.

    Reply
    • Thanks.

      I think I’ve certainly helped to create this monster with my unsubscribing.

      My average spam count into my Outlook email address per day is between 370 and 410.
      This has made me go back and look at my old (but still accessible) Gmail account which I hadn’t opened in 2 years – 126 spam messages in the inbox (I assume lots have been into and scrubbed from the junk folder automatically).

      Sort of underlines how much these spammers like to know they are bombarding an active email address.

      Every day a school day!

      Reply
  2. Hello,

    I recently became the target of a bitcoin scam and was quite amused at the level of threats and harm promised to my family. I determined my information was obtained during the LinkedIn hack of several years ago, even though the scammers claim to have compromising video of me and will send it randomly to my FB contact list.

    As others have pointed out one of your best defenses is to not open the email.

    About 15 years ago, I simply turned off the preview pane, and I have not had a spam email on my personal email accounts in over a decade. This helps because none of the code embedded that tracks that you opened the email is executed as the email is never opened unless I specifically open it.

    Some tips to stop phone scammers. I have turned off the voicemail and the ringer on my landline. Eventually they give up because there is no verification the line is active. If you can’t do this, when you answer the phone… don’t say anything and put the phone on mute to keep the line open. And if neither of these is feasible buy an airhorn.

    Reply
  3. The above article and comments have been very enlightening to me. I now understand (I think!) why some spammy scams are still getting through my AOL block. But as I live in the UK I am now also forwarding scam emails to report@phishing.gov.uk so that the Government’s anti-fraud team can have a go at them. The only problem is that to forward an email (in AOL anyway) you first have to open it. Not ideal!

    Reply
    • The best you can do is mark those emails as spam in the browser email window or email program and have AOL or your email program learn to recognize those kinds of emails as spam. Reporting them to a government agency is generally a waste of time as most scammers and spammers are from countries that don’t go after email scams.

      Reply
  4. In my hotmail I create rule and still it is coming through. I type in all these keywords, terms, small/ALL CAPS and still keep coming. I ruled it to delete it so I don’t have to bee dealing with that at all but to NA. Same address, same subject and on and on…. I wonder if these providers are doing it by them self on purpose, the sky is a heaven for corruption especially these days where honesty means nothing.

    IP address issue – in “view message source” it shows IP address. Some websites claims that spammers generate each time different IP address. Well, IP address for example I have is the same all the time so I can be tracked down like a dear. My service provider gave me the IP so it is recognized by their system as legitimate. I have no way to or do not know how to generate fake/alternative IP address recognized by my service providers. Spammers on the other hand do that apparently and providers recognize it as legitimate??? Don’t they have a tool to recognize an unauthorized IP??? In the PC world today I assume for security reasons each provider should be interested not allowing/blocking unrecognized IP addresses.
    There is something I am missing in this part why they get through and why no one is able to detect it. In certain circumstances the alfabet people should be able to track any digital process because it comes always from and through certain IP address appointed by the provider. Provider which sees unauthorized IP should be able to see from what actual IP address it is coming.
    Just a bit of mindjungle for me.
    Thanks for your attention.

    Reply
  5. It used to be that when you blocked a sender in outlook they were BLOCKED period. Now, it’s in no way effective and any and ALL unwanted emails go through no matter what. I thought it was outlook. However, they need to amp up their security and once again make it IMPOSSIBLE for spammers to get around the block. There HAS to be a way to permanently roadblock these predators. I terminated my Ebay account at least two months ago and unsubscribed from their mailing list AND blocked them yet I continue receiving emails from them in both my email inboxes at least three times a day. So frustrating.

    Reply
  6. My block senders list has not been working for quite a while. I just put in some addresses from recent spam messages. Looking for help, I found this page, and checked to see if any domain name was being obfuscated as you mentioned. I found one and went to the block senders menu to add it, and I discovered that the addresses I had just entered a few minutes ago were not there. And yes I had pressed Save.

    Is the block senders feature no longer supported for clients ending in cs.com? If so, how do I re-enable it?

    Reply
    • Depends on the email program you’re using. Whether it’s supported is almost irrelevant, as it doesn’t work on spam for the reasons mentioned in the article. Spammers make one email look like it’s coming from another, so you’re not blocking what you think, and they’re constantly changing email addresses, so blocking the current one won’t prevent the next one.

      Reply
  7. I suppose the real reason that Google, yahoo, and all the email companies do not effectively block spam is they have no incentive to do so.

    To me its a very simple fix
    1. No faking email addresses.
    2. No html accepted in the emails headers.
    Unfortunately, legitimate companies get marked as spam when the person signed up for the newsletters/mailings and changed their mind.
    But as long as these companies receive compensation, theres no incentive to do anything other than to pretend they are doing something.

    Reply
  8. The original question was, “How can I block addresses that come repeatedly to my junk email box? It says I am blocking email but it does not work.”. I agree with Leo that SPAM would go to the Junk folder, provided the spam detection is working. It is futile to block a spammy email address because as Leo said, they’ll get around. They usually start using a different FROM address. If you blocked all of the spammy email addresses, after a year or two you could end up with several hundred addresses in your blocked list.

    BLOCKING an address might work differently with each email client (or email provider). Some clients/providers might send BLOCKED emails to spam; others usually delete the emails before they reach the recipient. The difference between a BLOCKED address and one that is not blocked, might be different by one character (like 0 for O, or I for l). At a quick glance at a long address, a user might think BLOCKING is not working.

    Reply
  9. In Outlook, I have an Address Book of WHITE-LISTED email addresses. I also created a Rule in Outlook that delivers messages from ONLY those white-listed senders to my Inbox. Any message that’s NOT from one of those senders gets automatically redirected to a folder named “Unknown Senders”. Most of the messages that end up in the Unknown Senders folder are almost always spam. If I do find a non-spam message there from a new sender, I just add their email address to my White-Listed Address Book. Then any future messages from them will go directly to my Inbox. Everything else in the Unknown Senders folder can just be selected with Ctrl-A and deleted. With this method of screening for and accepting only white-listed senders, I get NO spam in my Inbox.

    Reply
  10. This was written a long time ago, but in my search for answers I came across it and I’m always interested in others thoughts.

    Blocking senders isn’t always futile, it can work, at least temporarily, and often that’s all that’s needed to improve quality of life.

    Many spam emails are random, but in my experience the worst offenders use the same domains. There was one a while back called mailcurry, I filtered anything from them to go to the bin. There’s another currently bulk spamming and I’ve filtered them too. As many spammers target the US market it’s easier for me to filter anything related to ‘auto warranties’, Walmart, target, Home Depot etc. I despise spam. I don’t mind scammers so much, their emails are often unintentionally funny and I love how the head of the FBI and American diplomats in Benin take the time to email me personally. Saudi Princes are so early 2000s.

    Reply
  11. My junk mail filter is working pretty well at sending spam to junk. However, now I get mostly “blocked” email, from new addresses, as you’ve explained. Should I unblock these senders so my filter will get better at redirecting them? Another thought – should I uncheck “enable blocked mail filters? Using yahoo and Mac.

    Reply
  12. As a follow up: I “unblocked” a couple of spams and sent to junk. All of a sudden there are no more blocked emails at all. Hallelujah!! They must have all come from the same spammer. Now yahoo’s recognition is almost flawless.

    Reply
  13. I have found blocking to be somewhat effective when dealing with marketers that are adept at changing their email formats around enough to get around spam filters even after I have marked previous messages from that sender as spam. One domain that seems to have a blanket back door to the inbox no matter what I do is ccsend.com. AKA Constant Contact. AKA spam service for people who don’t think they are spammers. Mail from people using these guys will always get through even after adding ccsend.com (and org, net, co, etc.) to the blocked list in the email client, the user’s profile in the spam firewall (currently Spam Titan after moving away from Barracuda), and the global block list in the firewall. At this point I can only assume they have paid to get a blanket whitelist status.

    Reply
  14. Blocking an email sender accomplishes nothing in Mac Mail. It’s not a matter of ever changing addresses or other spoofs, Mac Mail just puts a little block icon next to the sender’s name and sends it to spam. I still have to delete EVERY BLOCKED EMAIL. The “move it to the trash” setting doesn’t do anything. Very frustrating. Do spammers pay Apple a fee to avoid blocking filters?

    Reply
  15. This is by far the best site and discussion I’ve seen on unwanted Spam. Thank you.
    I must confess that I am a bit of a SPAM vigilante. It’s not enough for me to block, mute, mark as spam and delete, though I do understand the practicality of that, and the time I would get back if I handle it that way. I use Apple mail which is touted to be one of the “good” ones at recognizing and blocking SPAM, yet I get about 75 a day to an email address I never use (it was my apple id for years, I’ve since changed it but continue to get only spam to that email). I do send spam (forward as attachment) to: spam@icloud.com, abuse@icloud.com, reportphishing@apwg.org, phishing-report@us-cert.gov. I doubt it’s doing anything, but I wish it would. I don’t want to change my email address that I’ve used for years and have established for my friends, family, businesses, etc. It doesn’t seem like a great solution for me who isn’t doing anything illegal to evade scammers who are doing something illegal.

    Reply
  16. Byron Sevario
    February 18, 2011 at 4:04 pm
    I wish there was a way to destroy the computer that the email was sent from. I hate those Sex spams.
    But knowing that you can’t do that just keep deleting them. That works every time.

    I just came across this blog and above note from Byron Sevario.
    Actually it seems there is some way to destroy a computer, which I learned when complaining to my ISP’s Customer Service some years ago. The person answering my call gave me his private email address and asked me to contact him after work, which I did. He said to consider it a war and to imagine two tanks roaring down the road, promising that his tank (computer) would destroy the other, after which I’d never get emails from that guy again. True enough, after weeks of increasingly annoying and offensively personal missives I finally had peace. No idea how it was done and so sad I didn’t keep the guy’s name or email to even confirm his ‘win’ and thank him.

    Reply
  17. Most email programs and webmail sites block the senders when you mark them as spam. Blocking senders is not effective against most spam, but it helps a little. Just let your mark as spam button do the waking.

    Reply

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