Technology in terms you understand. Sign up for the Confident Computing newsletter for weekly solutions to make your life easier. Click here and get The Ask Leo! Guide to Staying Safe on the Internet — FREE Edition as my thank you for subscribing!

Why is my mail to HotMail (or AOL, Yahoo, etc.) subscribers not being delivered?


Whenever I send e-mail to Hotmail subscribers, they never receive it and it
never bounces back. I’m sending mail from my domain-based e-mail address
through my Netscape 7.2 e-mail client. In other words, it’s not a Netscape
account. Netscape is just the e-mail client, and I can receive and send other
mail perfectly. I only have problems with Hotmail. Everyone else seems to
receive my mail this way. This is driving me crazy.

Me too.

I’m one of the admins for a fairly large mailing list and we face this type
of problem frequently. Last week it was HotMail subscribers, but only those
that were signed up for the “digest” version of our mailing list. A couple of
months ago it was AOL users, but only some, and not always the same ones.

Our email infrastructure has become frighteningly fragile.

And it’s all because of spam.

Become a Patron of Ask Leo! and go ad-free!

If the email doesn’t make it through, and there’s no bounce message
returned, it’s likely that it was filtered as spam.

Now I can hear you screaming already: “But it wasn’t spam!!!”

I know, I know. That’s the terribly frustrating part.

The problem is that email recipients are also screaming. They’re screaming
“How do I stop all this spam?” And ISPs and email providers such as HotMail,
AOL and others, are scrambling to try and put into place solutions that halt,
or at least seriously reduce the number of spam messages that get delivered to
their customers.

The problem is that they sometimes go overboard, and mark legitimate email
as spam.

“There’s simply no way to guarantee that your email will
be delivered, or guarantee that you’ll find if it was or not.”

Now, “marking” it as spam is annoying enough, but if that’s all they did,
that’d actual be less of a problem, since we’d still be able to look at it and
decide what to do with it. Unfortunately, they’ve also taken to simply blocking
and discarding much of what they see as spam.

And naturally, “what they see as spam” is a moving target. In attempts to
improve the spam detection rate or react to the latest wave of actual spam,
most folks are continually updating and upgrading the algorithms they use to
tell spam from legitimate mail.

In the HotMail example I mentioned I pointed out that only mailing list
subscribers that were getting the “digest” version of our mailing list were
affected – folks getting the mailing list content in individual messages
continued to receive them without problem. HotMail had decided that something
about our digests looked like spam, and began discarding them. I assume they
got complaints, because about a week later, they suddenly began to be delivered

For a while AOL used a technique called “rate limiting” – meaning that it
would only accept so much mail in a certain amount of time from a particular
sender. If you were trying to send more than that, you were likely a spammer,
and the excess was discarded. What they failed to take into account were
legitimate mailing list servers hosting multiple mailing lists that were
attempting to send legitimate email across several mailing lists to a lot of
AOL customers that had explicitly subscribed and requested it. After a while
and many complaints, this technique also seems to have abated.

It sucks. Email providers are attempting to provide a valuable and
legitimate service to their customers by blocking spam. And yet in their
attempts to do so, they’re often over-aggressively blocking legitimate mail,
with no real recourse for legitimate senders.

So what can you do?

Well, I’ll start by saying that there’s no silver bullet. There’s simply no
way to guarantee that your email will be delivered, or guarantee that you’ll
find if it was or not. That’s simply the nature of the world right now.

But there are things you can do to stack the deck in your favor.

  • Don’t spam. I know, I know, you don’t. Even so, don’t do it. The key word is
    “unsolicited”. Don’t send people email that they didn’t ask for, and don’t put
    people on mailing lists without requiring double opt in. Anything less can get
    you legitimately branded as a spammer.

  • Do everything you can to avoid looking like spam. My previous article
    Why is my
    mail to this person not getting through?
    includes a short list of many
    common things that can make your email start to look like spam.

  • Check to see if your mail server has been blacklisted (not your PC, but the
    server that sends your mail – usually your ISP or your email service provider).
    Unfortunately this may, or may not, actually help you. There are so many
    different blacklists maintained by several entities, it’s difficult to know
    which ones actually matter, and which ones might be responsible for your
    delivery problems. Even worse, getting off of blacklists can be extremely
    difficult, but at least it might give you some clues as to what might be
    happening. I have known people to change mail servers rather than deal with
    trying to get off of blacklists. ISIPP (Institute for Spam and Internet Public
    Policy) has How
    Can I Find Out If My Email Is Being Blocked?
    which includes links to
    serveral blacklist checking services.

  • Check with the postmasters at the sites you’re having trouble with. AOL has, Hotmail has, and most other large ISPs or EMail
    Service providers will have contact addresses that will at least claim to aid
    you in getting your legitimate email through. Quite often they’ll have you jump
    through various hoops to do so – but remember, they’re also counting on the
    fact that spammers are unable or unwilling to jump through those hoops.

  • If it applies, consider using one of the accreditation services, or other
    email registries. While there’s no general agreement yet on a single solution,
    publishing “SPF” records for your mailer, using “DomainKeys”, or signing up for
    accreditation by a service such as SuretyMail can help get your
    legitimate email delivered, particularly if you are a large sender. If you use
    a third party email or mailing list service provider, you might investigate
    which of these techniques they employ.

  • Educate your users. One of the most frustrating problems mailing list owners
    suffer from is subscribers using the “This is Spam” button to delete or
    unsubscribe from legitimate email that they actually requested (and often
    confirmed via a “double opt in” email). If they requested it, of course, it’s
    not spam, and reporting it as such damages everyone.

As you can see, there aren’t many concrete steps that can guarantee your
email delivery. Without a bounce message telling you why, it becomes a guessing
game. The best steps to take when you encounter a problem are to simply make
sure that you’re being a good email citizen, track down what clues you can, and
possibly follow up with the ISP with which you’re having delivery issues.

Do this

Subscribe to Confident Computing! Less frustration and more confidence, solutions, answers, and tips in your inbox every week.

I'll see you there!

22 comments on “Why is my mail to HotMail (or AOL, Yahoo, etc.) subscribers not being delivered?”

  1. This is why I refuse to enable my ISP’s spam filter option — I want control of what gets flagged as “possible spam” and what happens to it, and “silently throw it into the bit-bucket” is not what I want. (I use other filtering options, but they’re under my control, not my ISP’s.)

    Unfortunately, I can’t choose what method is used by the recipients of any e-mail I send.

  2. Also unfortunately, some ISPs do additional filtering that you can’t control. Both HotMail and AOL examples in the article had nothing to do with user preferences – it was ISP systemic.

  3. This was very helpful. I have a cousin that I have been trying to e-mail but it does come back with a message. I have tried from my aol, msn, and yahoo accounts and it still bounces back. I will try what you have suggested.

  4. I maintain an email database for the company I work for. Another problem I often see is people using a “challange/response” system to stop spam (especially EarthLink users) but then subscribing to email lists. A challenge/response system sends and email back to the sender saying something like “In order to stop spam, member John Doe has requested we check that you are a real person and not a spam program sending bulk email. Please respond to this message to have your message delivered.” People do this without realizing they are also stopping the legitimate emails they signed up for because the mailing list system that sent the original message isn’t smart enough to know how to respond so the original legitimate message will be allowed through.

    Leo, I agree, it is very frustrating because people get mad at us for emails getting blocked by their ISP. Even some of the ones who have turned on the challenge/response feature provided by their ISP. There is a certain percent of the population who just don’t get it – those are the ones who get scammed by spam and illegitimate emails and it is the rest of us who end up putting up with the consequences.

    On the issue of users who delete mail by marking it is spam, part of the problem there is the person creating the email message sometimes hasn’t made it easy enough to opt out of the mailing list. I can’t tell you how many times I have seen the unsubscribe instructions at the bottom of an email in such a tiny font that it is all but unreadable – making it impossible for readers with less than perfect vision to read the unsubscribe instructions. This text should be as easy to read as the rest of the text in the email.

  5. I’m a secretary for a chapter of the CMA A(Christian Motorcycle Association) and I send many group e mails. All of a sudden, all aol addresses are causing an error, like aol is blocking me from sending to their people. They won’t help me and the Earthlink people are suppose to be contacting them on my behalf, but as time goes by, nothing is being done. I’ve checked the postmasters explanation and it looks like according to them, I’ve met a quota of too much email being sent. Very frustrating and making me not able to do my job.

  6. We are still fighting just to hear from Hotmail. They will simply not respond to my emails to request reasoning why theya re blocking my mail server that is not a relay and only has 12 domains on it. I have monitored the mail and it is now way an excessive amount. They simple refuse mail from my sever’s ip.

  7. Just thought I would chime in here. I work for a online social network and we send millions of mail on a daily basis. Both newsletters to legitimate users as well as relay from legit users to other users are processed through the same mail cluster. Hotmail has caused us to re-architect parts of our mail cluster because, like mentioned in a previous post, hotmail has deemed legitimate mail from our host(s) as spam despite all our efforts to reform mail headers, educate users, enroll in hotmails “Junk e-mail” reporting program and “Smart Network Data services”. Yet we STILL get blocked on a daily basis. What’s missing I ask? Well, simply put, we have not paid the $20k fee to the 3rd party “sender score certification” program So while we wait the 90 days for this to process, I have stumbled across an error we get in the mailer logs that has helped us in curbing the block rate by hotmail and I hope it will help you too. (I am using Port25’s PMTA v3.2) The error is related to Hotmail’s rate limiting and thus can be curbed by configuring your sending agent to reduce the amount of mail that is being sent once it receives this error:
    2007-01-25 11:26:28 SMTP service unavailable: “421 The mail server IP connecting to Windows Live Mail / Hotmail server has exceeded the rate limit allowed. For troubleshooting information, go to“ received from ( while connected from ( to (

    with this error now in my armory, I was able to configure our mail server to detect this error, and once detected, set the application to go into “back-off” mode, and send only +n number of messages per hour. Since there is no way to tell what the rate limit is set to on hotmail’s servers, it has been a trial-and-error thing. This has prevented us from being blocked, but of course will increase the amount of time it takes to deliver a message…but it will get there.
    Hope this helps some of you out there having the same issue.



  8. Hotmail has a horrible system in place. We send millions of e-mails and I can say that AOL is the “benchmark” of postmasters. As a tech guy that used to hate AOL as a service, I LOVE AOL because of how brilliant they handle postmaster requests. AOL even has postmaster phone support with no hold times! Hotmail.. with their dodgy systems and ignored requests.. no phone support… nobody to help… can’t make heads or tails of what’s going on.

    Only Hotmail will delete e-mail at the router… AOL sure doesn’t. if you’re blocked at AOL you get a nice little 421 error and a link to tell you exactly why you are being blocked for EVERY email. THANK you AOL.

    MSN/Hotmail would probably staff a few more people in the postmaster department if the word got out they were censoring email and people started switching to the new FREE AOL… SPREAD THE WORD!

    Hash: SHA1

    My experience with AOL has been exactly the opposite of what you’re

    People fail to get email that they’ve requested, and without
    notification to either the recipient or the sender. AOL has been
    particularly UNhelpful in helping the organizations I’ve been dealing
    with. As a result we’ve basically given up trying to get AOL to work. We
    now recommend to our members that they use an email account other than
    an AOL account.

    Version: GnuPG v1.4.6 (MingW32)


  10. I had a great experience with AOL getting removed from a spam list b/c of a hacked mail form. Now yahoo and hotmail were horrible… i still cannot get them to allow my mail through… also hotmail nor yahoo even respond… AOL required a single phone call and w/in hours i was receiving mail again. AOL postmaster is the best i have dealt with yet.

  11. Your article is interesting all I’m trying to do is get in touch with my niece at time I try it won’t go through.I have multiple sclerosis and can get confused.Need a simple answer.

  12. I checked the error code I was getting under search…aol 554. Seems my aol friends were not getting my messages..Daemon Mailto returned…Found out I had a signature on my e mail and their account did not accept attachments. I took off my signature..under options on my yahoo page and now all goes well. Just check out the error code you are getting and maybe you can figure yours out as well

  13. It’s a shame that spammers have ruined the email system. It’s even more a shame that legitimate companies can not get their subscribed emails through, BUT, I have to say that a lot of the legitimate companies cheat a little too, and when they get caught at it they seem to complain the loudest while excusing their behaviour. One client I worked for actually got mad at me because I would not punch a hole in my personal email system for his service. I told him was under total user control and if they wanted his stuff they would get it. Came to find out what he was calling legal was purchasing mailing lists. We all know that most lists are scraped from tons of illegitimate sources and so I will end this with a person peice of advice. If your email service is getting blocked you need to be more legitimate than you already think you are. As for me I get all the spam protection I need from my current provider, and believe me when I say I ONLY GET WHAT I WANT.

    Please try and remember something. Email was meant to improve the quality of life, not become a platform for floods of spam just because you dont have to pay to send it.

    Configure your mailers to use true and accurate headers
    Provide a legitimate automated and easy to use unsubscribe link
    Make the link CONSPICUOUS!!!

    Remeber if you don’t offend the recipient in the first place you will stand a better chance of not getting reported.

  14. I am using a quite legitimate email address and have definitely done nothing to have these people at Hotmail block my emails to private recipients.

    It is disgusting that these companies can be so heavy-handed and able to take cart-blanch action to interfere with personal mail.

    Up to this week all my emails have been getting through and there has been absolutely no reason for this to have happened.

    It is a pity that legal action cannot be taken against these parasites for dealing out unwarranted punishment to innocent people.


  15. I can access the MSN home page but I cannot get to the log in page it is completely blank. So I am unable to sign in. Whats the problem?

  16. We are one of an exchange group. I have just been blocked by MS Hotmail. I see MicroSoft are behaving with software like Apple with hardware. They are the only ones who know what is best for you. FredL

  17. why is my yahoo mail always going in my hotmail inbox,getting nothing in my yahoo at all i,ve tried everything even a new yahoo account but still going in my hotmail driving me nuts HELP !!!!!

  18. @Sheila,
    I don’t think there’s any way that can happen unless you are somehow setting up a forward from the Yahoo email. You must be accidentally setting that up in the account, perhaps when you are trying to put in a recovery email – maybe putting it in the wrong spot.

    Just a guess.


Leave a reply:

Before commenting please:

  • Read the article.
  • Comment on the article.
  • No personal information.
  • No spam.

Comments violating those rules will be removed. Comments that don't add value will be removed, including off-topic or content-free comments, or comments that look even a little bit like spam. All comments containing links and certain keywords will be moderated before publication.

I want comments to be valuable for everyone, including those who come later and take the time to read.