Email Server Blocks at various websites

Posted on 2006-11-02
Last Modified: 2012-08-14

Apparently somone on my network has a email worm virus, and has got me on some ban lists.  I am trying to find the infected computer, but have not been able to yet, but I blocked access to port 25 from everyone in my network except the mail server.  

 I recieved this error when I tried to send out an email to a hotmail user.  
550 Command rejected for policy reasons. For troubleshooting information, go to

How do I fix the issue to send out to hotmail users again?
Question by:Tom_Hickerson
LVL 10

Assisted Solution

kgreeneit earned 250 total points
ID: 17861379
hi there, you need to go to this website and enter the ip address of your mail server in the spam database checker to see if you are blacklisted. It should give you contact details of the blacklister and information on how to get yourself unlisted.

hope this helps!
LVL 20

Expert Comment

ID: 17862197
That happend to us but it was not a virus...we were sending mass emails and we forgot an unsuscribe link and we were banned from hotmail, yahoo and aol we had to comply with their policies. also it looks like something was wrong with our dns settings. also check that your exchange was not use for NDR spam

Expert Comment

ID: 17862711
Hotmail now have new policies on accepting mail from mail servers.

They will not accept mail from a mail server that does not have a  SPA record in their DNS.
Check that your DNS for your domain contains a TXT entry with SPA information.

Author Comment

ID: 17862790
what is spa and do I do that with my registar?
Why You Should Analyze Threat Actor TTPs

After years of analyzing threat actor behavior, it’s become clear that at any given time there are specific tactics, techniques, and procedures (TTPs) that are particularly prevalent. By analyzing and understanding these TTPs, you can dramatically enhance your security program.


Expert Comment

ID: 17863023
sorry ... my typo .... I meant SPF.
This is a DNS entry for your domain name.

If your mail server was
then a typical entry would be
mail    TXT   v=spf1 mx ptr ?all

Author Comment

ID: 17866630
where do I add/edit this info at?

Expert Comment

ID: 17871142
You would add it like this...


Accepted Solution

Kyanar earned 250 total points
ID: 17872847
"Hotmail now have new policies on accepting mail from mail servers.

They will not accept mail from a mail server that does not have a  SPA record in their DNS.
Check that your DNS for your domain contains a TXT entry with SPA information."

This is not correct.  Hotmail will still accept email from any valid SMTP server, provided it has a reverse DNS entry.  SPF records are NOT required, but when in place will actually cause the Junk Mail filter to be less likely to consider your email as spam.

Reverse DNS entries are probably set up by your ISP, so it is unlikely to be that.  Also possible, is that a machine on your network attempted to open more than 500 simultaneous connections to a Hotmail server, which triggers a block.

Visit for assistance, and an email you can contact to find out what you can do.

Featured Post

Highfive Gives IT Their Time Back

Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

Join & Write a Comment

Introduction Often we come across situations wherein our batch files would be needing to reboot Windows for a variety of reasons. A few of them would be like: (1) Setup files have been updated whose changes can take effect only after a reboot …
Many people tend to confuse the function of a virus with the one of adware, this misunderstanding of the basic of what each software is and how it operates causes users and organizations to take the wrong security measures that would protect them ag…
Access reports are powerful and flexible. Learn how to create a query and then a grouped report using the wizard. Modify the report design after the wizard is done to make it look better. There will be another video to explain how to put the final p…
In this tutorial you'll learn about bandwidth monitoring with flows and packet sniffing with our network monitoring solution PRTG Network Monitor ( If you're interested in additional methods for monitoring bandwidt…

705 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

16 Experts available now in Live!

Get 1:1 Help Now