Cannot send emails to email addresses

Due to some reason, we cannot send emails to the email address. It comes up with the following error (I have hidden the user details due to security reasons):

The following recipient(s) cannot be reached: on 04/11/2008 14:52
            There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
            < #5.5.0 smtp;550 OU-001 Mail rejected by Windows Live Hotmail for policy reasons. Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation problems. If you are not an email/network admin please contact your E-mail/Internet Service Provider for help. Email/network admins, please visit for email delivery information and support>
Any suggestions, what can be the problem. Our domain is not listed in any blacklists and mail server has a reverse DNS record setup correctly. Please help.
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>Reasons for rejection may be related to content with spam-like characteristics or IP/domain reputation problems.

your sending ip address seems to be treated as spammer address, thus they don't accept e-mails from you. Try to contact them and clarify the issue:
MSWarriorAuthor Commented:
Thanks for your comment Kukno.

I have checked our IP in the spam lists ( and have also checked with the ISP, it is clean. I have sent an email to requesting further clarification. It's quite funy as I have tried sending messages to few users and it works but it doesn't for any users. Any more suggestions?
>Any more suggestions? is just one RBL list. As you don't know how they configured their Anti-Spam System, your only real chance is to communicate with them.

Here are some other things to check:

1.) Is your DNS properly configured, i.e. does it contain a PTR Record for your sending IP address that "points" to the same name as the MX Record for your domain. Some mail systems do check this.

2.) Check you IP address on more RBLs

Try other "google: multi rbl check" tools.

3.) Use a different IP address to send e-mails.

4.) Ask your provider if he can provide a "smart host" for you.


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MSWarriorAuthor Commented:
Thanks Kukno,

I am really sorry for the late reply.

1.) PTR records -  I was checking your first suggestion and found out that the PTR record points to, whereas the MX record for our domain points to the

2.) I have checked our IP on the suggested website, and it is not listed.

Haven't tried 3.) and 4.) yet.

Please suggest on the above.

>Please suggest on the above.

well, change your MX record to

AND you should really contact the postmaster of the recipient and ask why your e-mail was blocked. Otherwise you end up trying to change all kind of things without success.


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MSWarriorAuthor Commented:
Thanks Kukno,

I have changed the MX record and it seems to be working fine now. We were having problems with AOL and even that is fixed. I will def accept ur solution.

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