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Most email programs have the ability to block email from a specific address. Unfortunately blocking a sender it an ineffective way to block most spam.

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

Blocking is 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 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 means in your email program; telling your email program nothing more than "when email from this sender arrives, just put it in the junk folder".

"... using sender blocking to stop spam is a waste of time and effort."

That's one definition of blocking.

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 of the ways that they do so is to make email addresses 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 <>

There you can see the display name, "Leo A. Notenboom", and the email address,, and it's pretty obvious which is which.

The display name is optional, but if it's present, many email programs will only display it, and not the actual email address by mistake. 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 over that, or perhaps click on it.

Spammers do this:

From: <>

Here the display name is "", but the actual email address is "<>". In some email programs, what you might see is this:


It looks like email from, but it's not.

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

Ever-Changing Email Addresses

Because spammers can manipulate the "From:" address so easily, there's another technique they use that also 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 they next spam that comes from a different address. Or the one after that. Or the one after that.

Couple that with the tricks that 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.


Don't block.


Most email programs, and almost all web-based email services, have the ability to mark emails as spam. This then 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.

Google's spam filter as used in Gmail seems to be particularly effective these days.

If that doesn't work, then my suggestion is to relax and just use your Delete key. It's simple, quick and 100% accurate.

Is Blocking Good For Anything?


Blocking 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, then 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.

Article C4731 - February 2, 2011 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

February 8, 2011 9:02 AM

One approach which takes time, but seems to work is to identify the isp from the headers and complain to them. Several tiresome spam mails sent many times have stopped after I reported their activity to the ISP. Only works with reputable ISPs

thomas smith
February 8, 2011 9:11 AM

hi , i agree that the block option is not perfect but in hotmail it works for me mostly. I just delete the junkmail folder all at one time. also the sweep option helps a bit

Alex Dow
February 8, 2011 9:35 AM

Check whether the JUNK Directory can be set to Delete IMMEDIATELY or after a given period such as 7 Days with my ISP.

I have mine set to the "7 Days" Option; but I do go in about three times per day, do a quick check occasionally to see if there are any genuine messages - then Delete them en-bloc, ie a single instruction gets rid of 500 messages etc.

Byron Sevario
February 18, 2011 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.

November 23, 2011 10:05 AM

cannot block a blackberry message.need help.i use windows mail

April 22, 2012 10:25 AM

In Hotmail, email blocking does NOT work! It seemed to for a while, but recently emails I have specifically blocked come right through. Contrary to your article, they have not been change to cleverly get through, but are exactly the same. Is this feature defective?? What do I do? Thanks..

June 9, 2012 10:21 AM

The problem with the coming back mails in the junk that you already ''sweeped'' and ''blocked'' is the following :
you can sweep and you can block mails that you can direct to your Delete mails, or even not to come back ever, is that Hotmail have a capacity of only '500' mail to block under Options/Safe and blocked senders !
Anything more shows you during sweeping that it is blocked but in fact it is not !!!
Under Options also, for the rules of sorting messages it has also a limit on the number '250' if i remember and then it stops redirection of mails.
Nowadays you need at least a good '2000' capacity to limit what you receive and Hotmail is not expanding it.
Already i mailed Hotmail on that but the answer always : How to sweep and it is a false statement because of the lomit on the volume to sweep.

Najam Bhutta
February 14, 2013 10:50 AM

Microsoft software engineers write all kinds of programs in the field but how come they can not write a program that can block spammers. I think they do not want to do it purposely. Probably, they have financial interest.

February 14, 2013 4:05 PM

The problem is that the spammers are also good programmers. They are, by the very nature of what they are doing, always ahead of the anti-spam guys. Same thing with malware writers.

The bad guys think of a new way to get through the system, and then the system engineers have to first discover the breach, and then write a new block. So the spammers are always ahead of the game because they are creating the game.

You are absolutely right that they have financial interest. Unfortunately for us the "They" are the spammers. They do it because it works and they can make a lot of money from it.

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