On my website, I send an automated email using libmail.php for new sign-ups.

Users put in their email address and they are sent an email to activate their account.

This usually works for Gmail. However when a user signs up with Outlook.com, no email gets through to the user.

In my PHP code (libmail.php), I actually have done a BCC to another Gmail account from which I am sure that the activation email was indeed sent to the user, but it doesn't reach his Outlook.com email account.

Is there anything that I can do about this?

  • Have you checked your domain name and IP address in mxtoolbox.com/blacklists.aspx??
    – closetnoc
    Apr 25, 2015 at 4:09
  • oh no! it seems to be blacklist. Thanks for the information. How do i remove it from the blacklist?
    – Shanker
    Apr 25, 2015 at 4:18
  • When you look it up via that website, somewhere there is a link on how to remove it from the blacklist. Each blacklist is different of course, but most will allow an entry to be removed. Do the lookup again (if you need to) and look for a link. It has been a while so I do not remember where it is. But it is there somewhere- perhaps under details or something like that...
    – closetnoc
    Apr 25, 2015 at 4:23
  • Thank you so much! Without your help i wouldn't have identified the problem. Appreciate it a lot!
    – Shanker
    Apr 25, 2015 at 7:11
  • Add that as an answer, it looks like this question is unanswered now ;)
    – William
    Apr 28, 2015 at 8:19

3 Answers 3


See closetnoc's comment for how to fix specific problem you are running into.

Generally, if you send emails with Mandrill or another similar site for programmatically sending emails you don't have to worry about keeping yourself off blacklists and other things like that as the email sending service will manage it for you.


I agree with closetnoc as well that you should use mxtoolbox.com to check your domain name and IP address to see if you are listed on a blacklist and if you are, go through each entry and visit the respective websites to find out how to be taken off the blacklist.

This can happen because hackers may have installed a malicious script that is executed sometime when the main script (such as index.php) is run. The malicious script could then read an email address from a local database and send a special message to it. This then produces spam. I'm not sure how frequent the scripts are executed because I'm not a hacker myself, but that's about the gist of it.

Another thing to check for is outlook settings to see if your domain is blocked in the software itself. If you still have issues, then you may want to contact the microsoft team to rectify outlook problems.


Check your bounce-backs (via "view original"), serv mail queue, and mail delivery reports for 2 things:

First, AOL, Yahoo, Live, Hotmail, Outlook, and others will block mails without proper DKIM and/or SPF records. There will be a reply, but i dunno what error code they use. This is because a domain without those records can be more easily spoofed, so it's more or less mandatory to set one or both if you wanna send out mails. More about SPF here.

Second, ATT, sbcglobal, frontier, bellsouth, and others under ATT will block legit IP's all the time, even when they have DKIM and/or SPF. This usually returns a 521 error and some words about DNSBL:ATTRBL [failRBL]. Microsoft (hotmail, outlook, live) does this too occasionally, so make sure that you aren't getting some kinda RBL message back. If you don't see a bounce message back, check the serv side logs for clues. I dunno if this email is still valid, but MS can remove blocklist IP here: [email protected]. If you need the ATT realm one it's here: [email protected].

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