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What Happens When I Mark Something as Spam?

Question: When I get an email from someone that I do not want to ever hear from again, I report it as spam. What really happens to it? Does my email service know what to do with it if it ever shows up again? Is there any protection for me? Does the person that sent the email know that I put it in the Spam folder?

There’s no definitive answer on exactly what happens, for reasons I’ll explain in a moment.

However, some general concepts apply when you mark something as spam.

The first thing we need to know is whether you’re marking it as spam in an email program running on your machine, or if you’re using an email service’s web-based interface via your browser.

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Marking spam in your email program

An email program is software that runs on your computer and downloads messages from your email service to your local hard disk. Examples of these kinds of email programs include Microsoft Office’s Outlook, Thunderbird, Windows Live Mail, and the Mail program included with Windows itself. There are dozens, if not hundreds, of others.

When you mark something as spam (or “junk”, as it’s called in some programs), you are typically telling only that program that the email message is unwanted. Particularly if your email account is downloaded using the POP3 protocol, the information about what you’ve marked as spam typically does not make its way back to your email service provider. The result is that it does not affect what email will continue to be downloaded in the future.

Dedicated email programs and IMAP

SpamMobile devices have added a couple of twists on whether or not marking something as spam in a computer-based email program will actually make it back to the email service.

Some email services now provide dedicated email programs. On my mobile phone, for example, is an app I use to access Gmail. Technically, that’s an email program (app) running on my computer (the phone). However, since it’s dedicated to handling Google Mail, when I mark something as spam using the program, the information is transmitted back to Google’s servers. Similarly, I have the Outlook mobile app, and when I use it to mark something as junk in my Hotmail account, that information also makes its way back to Microsoft’s servers.

IMAP is used in desktop email programs to allow you to access your email from multiple different devices and keep everything in sync. IMAP does this by leaving the “master copy” of your email on the mail server, and simply maintaining a synchronized copy of your mail on your computer. Change, delete, or move mail around in folders on your PC, and those changes will also be reflected in the master copy on the mail server.

When you mark an email as spam, some email programs simply move it into a spam or junk folder. If you’re using IMAP, when the move is reflected on the server’s master copy, it may be enough to notify the service that this message is spam.

There are no blanket rules, and – aside from dedicated apps, like the Gmail and Outlook apps – it’s difficult to make assumptions about exactly how your email program works with your email service when it comes to spam. The best I can suggest is to check the help information available for each.

How email programs use the information

An email program may use the fact that you’ve marked something as spam in several different ways:

  • It might add the sender’s email address to a block list. (This is a separate function in some email programs.) Unfortunately, block lists based on email addresses are typically not at all effective in the war against spam – spammers are constantly changing or faking their email address.
  • It might add the IP address of the sender (or the sender’s email service) to a block list. Once again, IP-address-based blocking is also not effective against spam; spammers send from millions of different IP addresses.
  • It might analyze the contents of the message and identify various characteristics of the message it then records as “looking like” spam to you. When more email arrives with enough similar characteristics, it might be automatically flagged as spam. This is the most common, and currently the most effective, email-program-based, spam-filtering technique.

As effective as it can be, the problem with looking for characteristics is that it’s difficult to predict what will or will not constitute spam. You might get an email that is clearly spam to you, mark it as spam, and then later get another nearly identical message that was still not filtered.

These types of “learning” or adaptive filters don’t necessarily act immediately, but build up statistical characteristics of what spam looks like to you depending on additional factors, like the number of times you mark similar messages as spam. It might not be until the second or third (or fourth or tenth) time you mark a particular type of spam that the filter will have enough confidence to kick in and automatically identify similar messages as spam in the future.

“Similar” is, after all, a fuzzy concept.

What email programs do with spam

Great, your email program has successfully identified something as spam – now what does it do with it?

As I discussed above, most email programs do nothing more than move the email to a Junk or Spam folder. That’s it. Period.

There’s no notification back to the sender, and no notification to the email service. Everything happened on your computer and only on your computer.

This type of spam filtering is nothing more than placing email detected as likely being spam into a different folder as it’s downloaded to your computer.

Marking spam on an email service

If you’re using a web browser (like Internet Explorer, Chrome, or others) to read your email, you’re using an online email service. Your email is stored “in the cloud,” not on your PC, and you’re simply viewing it via a web-based interface.

Examples of web-based email services include, Gmail, Yahoo Mail, and many, many others. Your own ISP or email service provider may also have a web-based interface for your email, in addition to the services that allow you to access it via your PC.

The important thing here is that you’re using your web browser to interact with your email stored on your email service’s server.

How email services use the information

When you mark something as spam on an online service, you’re doing essentially the same thing you did above with a PC-based email program – you’re telling the service, “I think email that looks like this is spam.”

The difference is that you and every other user of that service are all telling the provider what you think is and is not spam.

Exactly how the service provider uses that information is a mystery, and that’s on purpose.

For one thing, they don’t want spammers to learn the details of the mystery; that would make it easier for spammers to know how to work around it. For another, how service providers use that information is constantly changing in response to the ever-changing nature of spam.

There are several approaches email service providers may or may not use:

  • Things that you mark as spam are used to identify and filter spam only for you. This is basically the PC model at the server level – you’re not impacted by the spam decisions of other users.
  • Your marking something as spam goes into a single database used for everyone. Only things that everyone thinks look like spam are actually filtered. No matter how often you mark something as spam, if everyone else on the service treats it as legitimate, you may never see it filtered.
  • Hybrid: a combination of what everyone thinks is spam plus what you think is spam is used when filtering email destined for your Inbox.

My sense is that it’s mostly the later, hybrid approach, but as I said, it varies from provider to provider and changes over time.

What email services do with spam

Much like the email program on your PC, when spam is filtered by an email service, it is typically sent into a junk mail folder in your account. You can usually safely ignore that folder, and/or periodically check it for false positives.

No notice is sent to the sender. The email has, in fact, been delivered; it’s just been delivered to your Spam folder.

Some services take things a step further.

Some services identify spam at a global level – perhaps based on content or source or something else – and block it from being delivered entirely. You’d never see it in your Inbox or in your Spam folder. From your perspective, it’s like the email was never sent.

Occasionally, in these cases, the service sends back a bounce message to the sender.

Maybe. Once again, there’s no guarantee.

False positives

Regardless of whether you use PC- or web-based email, spam detection is an inexact and ever-changing science. You’ll see email that you consider to be spam – perhaps even obviously spam to you – be delivered into your Inbox.

So, you mark it as spam and your email program or service learns a little more about what you consider to be spam. Occasionally, however, legitimate mail will get marked as spam and be filtered. This is referred to as a “false positive.”

For anything that’s been filtered and placed into a Spam folder, you should have the ability to say, “This is NOT spam”. This is perhaps even more important than identifying spam.

Once again, the program or service takes this indication from you and learns from you that email like this should not be considered spam.

That’s an important step to take. Every so often, spend a few minutes in your Spam folder looking for things that were filtered and should not have been. Mark those as “not spam” to reduce the chance of similar mail in the future also being filtered.

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31 comments on “What Happens When I Mark Something as Spam?”

  1. >I am on AOL and when I get an email from
    >someone that I do not want to ever hear from
    >again, I report it as spam.

    Spam reports should be limited to real spam, not people you just do not want to hear from again. If you subscribed to a newsletter, for example, unsubscribe don’t report it as spam.

  2. Hi Leo
    Might it not be worth mentioning the activities of internet security programs in this context? I use Kaspersky and it has certainly taken a view on email spam in the past and I have had to edit the reports on occasions to stop it marking stuff that is genuine.

  3. AOL and blacklisted my web address some time ago. It only affected their subscribers, and eventually an IT savvy pal got the blacklisting lifted. I don’t know if my e-mail address was spoofed, or why the blacklisting was imposed – AOL won’t say.

    Then another ISP blacklisted my web address, but that has been lifted as well.

  4. A good resource for people to learn about SPAM and how to prevent it is the excellent website by Randy Cassingham that can be found at… Between this and Ask Leo, you can’t find better information on the internet…

  5. In reply to Ronny’s statement – Be very careful when unsubscribing. In the past I have unsubscribed to some emails – and all that does is confirm they have a live one, and start selling your email address to other sources (I sometimes use different upper/lower case combos when I register – so I know what sites do it – and it can happen with quality sites). If it is unsolicited, I will mark it as spam. I will only unsubscribe to sites that I have subscribed to in the first place that I believe are not going to sell my address.

  6. With my Mail Provider/ISP, I can insert e-mail addresses that are either Accept or Reject.

    Originally, my impression was that the lists could only accomodate specific addresses on the lines of-

    Fine if only one person; but a nuisance if several were involved, gradually changing as individuals left and joined that company, so tedious to update.

    Recently, I found that the lists could accomodate all of the company employees by using the generic part of the address, ie-

    Proven to be very usefull.

  7. I use Thunderbird. I created a filter that puts all email from people who are not in my address book into the Junk mail folder.

    I find that more effective than marking something as spam, as the spam filter might take a while to learn that it is spam. Periodically, I’ll scan through the Junk mail to see if there is something legitimate.

  8. A lot of spam these days has my own address spoofed into the From: field.
    Is there (or can there be) detrimental effects of marking “yourself” as spam? I know a lot of programs / interfaces will not let you blacklist yourself, but this is different.

      • Most email programs or webmail interfaces won’t let you block yourself. If you could, it would cause programs to block your own legitimate emails. The only effective thing you can do is mark that email as spam and train your spam filter to recognize that kind of email as spam. That wouldn’t be a problem as it analyses the contents of the email and doesn’t block the address,

  9. It’s only a concern if that provider use address based spam filters, like did a few years back. It kept blacklisting my ISP as a source of spam. On several occasions I needed to contact my ISP and ask them to sort out things with aol. It worked for a few days, then it was back at the beginning.
    If they use a sane spam filtering technology, it supposed to know that the from and return addresses from spam must be assumed to be faked.

    • The problem is that you don’t know whether or not they block addresses. They may send any email from you to yourself to the spam folder.

  10. I would love it if Gmail added a layered approach.
    1) Violates some spam triggers – put in spam? group for the user to check.
    2) Violates more spam triggers – put it in the current spam group
    3) Items in spam group that have been additionally marked by users – use to train system for complete blocking and possibly to send bounce messages to sender.

  11. You have yet to tell me if an online email service automaticly places any re-occuring email address I’ve already marked as “junk” into my junk folder or my inbox folder. In other words, will I don’t want to see an email address that Ive already marked as junk come to my inbox folder again?

    • And, as I’ve said in several places, blocking an incoming email address doesn’t work – spammers keep changing the email address from which they send their stuff. It won’t take effect immediately, but eventually if you mark something as junk enough times the system should learn that this is junk to you and automatically send it to spam. How many is “enough”? There’s no way to know. The situation is significantly more complicated than just the from address.

      If you actually have an individual that IS sending from a specific email address, then depending on your email program you can set up a rule or filter to automatically delete those emails. Exactly how you do that, or whether it’s even possible, depends on what program and/or email interface you use. But like the spammer they can then still get to you by sending “from” a different address.

  12. I recently used OOPLA speed test and at the top of the web page it clearly said it was going to share my details. I ignored that and used the service. I immediately started getting 100+ SPAMS per day. Why would they do that. ???

    • That’s why you should always use a throwaway address when signing up for anything you are not absolutely sure about.

  13. I have someone emailing me that i dont want contacting me. How do i get an email address blocked from contacting me all in general?

    • Email programs and email websites have filters you can set to block senders from specific email addresses to by either sending those emails to the spam or trash folder.

  14. I recently purchased spam filtering software from MAILWASHER PRO. Their website indicates the program will intercept your e-mails and then you can choose which ones you actually want to have forwarded to your inbox. I have been disappointed in this programs effectiveness. Most e-mails continue to my inbox without having been intercepted by Mailwasher, and even those that do appear on the Mailwasher program, after clicking on their Wash Mail button, the e-mails still appear in my inbox. In other words, Mailwasher has not stopped spam from getting through as is suggested on their website. Would not recommend this software.

  15. You have commented on a great many iterative variations. But I saw no mention of some way of physically stopping e-mail from a specific source.

    My Example: A male and female with some kind of relationship started sending me e-mails. Often they were sending me 2 t0 5 emails “””Each” in a single day. The emails contained political news. None of their e-mails had a means of contact or unsubscribe.
    I sent then both (by using the reply option) 6 consecutive e-mails with a large banner asking them to please stop sending me e-mails.
    I had to do it 3 o4 4 days to get their attention. One of them sent me an e-mail saying “”their program did not allow them to delete anyone Sorry”””
    The emails kept coming. I strongly resent being forced to create a filter to prevent receipt of their emails.

    Normally I have very little problem with spam and just mark it Junk and I don’t see it again.
    I want a method of stopping them at their IP provider which in this case was I sent a complaint to Verizon and eceived a Mail – Damione notice of rejections Verizon would not accept it as I did not use Verizon.

    I started forwarding all their mail to [ FCC]. In researching, my understanding is the FCC does not address ordinary personal complaints about Spam.
    I did it anyway. Four, 5 6 forwarded mails a day to the FCC for over 3 – 5 weeks.
    It may be premature on my part, but I have not received any emails from the two addressees for two days. While I never had a day pass for the last 4 months I didn’t receive emails, I will not feel confident the problem is gone until at least 2 weeks pass with no emails.

    The other problem is there should be a way of stopping the propagation of crap e-mail and not just have to resort to an digital defense.
    Until the spam scum are punished it isn’t going to diminish.

    • There’s no way to stop spam at its origin. If you are continually getting spam from the same source, you can set a rule in your email program or webmail page to send all emails from that sender directly to the Trash folder. I did that for the email address of a “friend” who constantly sends out article reprints to support his conspiracy theories. That was a few years ago and I have no idea if he is still sending them out.

    • Technically there is no way to stop someone from sending you an email. In your case I would create a rule in my email program that automatically marks their email as spam, or even automatically deletes it so I’d never see it if it did arrive. The only other option is to complain to their ISP, but it’s unclear if they’d take action.

  16. With a broad title like that I want to ask “in my android phone, what happens when I ignore a call and them mark (is it the message or the call itself and therefore the caller?) as spam?

    • All email travels through the cloud (the internet).

      PC-based email programs include: Microsoft Office Outlook, Thunderbird, Pegasus, Windows Mail, and many, many more.

      Cloud/web-based email interfaces include:, Gmail, Yahoo mail, Proton mail, and many, many more.

  17. This is ridiculous.. If the spam addresses are noted ( I know they sometimes change but most don’t) then the manufacturers of the phones should be able to filter the offending articles we have bothered to point out for them as part of the phones programming.. We don’t have to deal with the whole internet’s tricks just our own devices..
    I hope I’m not now going to have to deal with more spam when this data is potentially stolen/sold, by the provision of my details.. To be clear,not accusing you of such.. bigger fish than you have been caught in the net..


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