Blacklisted by Hotmail but OK with Gmail/AOL

First of all, amazing script. It would've taken me a ton of time to write, but 
I had this up and running in a matter of minutes.

I currently loop through names trying to validate them on different common 
email domains -- Gmail, Hotmail, and AOL.

This worked for a little while, but Hotmail seems to have banned me. I'm 
wondering how to get around this.

I receive this message from Hotmail:

try mx2.hotmail.com:25
<<<
220 BAY0-MC1-F53.Bay0.hotmail.com Sending unsolicited commercial or bulk e-mail 
to Microsoft's computer network is prohibited. Other restrictions are found at 
http://privacy.microsoft.com/en-us/anti-spam.mspx. Sun, 6 Apr 2014 10:43:00 
-0700 
>>>
HELO (my domain)
<<<
250 BAY0-MC1-F53.Bay0.hotmail.com (3.19.0.77) Hello (my IP)
>>>
MAIL FROM: <no-reply@(my domain)>
<<<
550 SC-002 (BAY0-MC1-F53) Unfortunately, messages from (my IP) weren't sent. 
Please contact your Internet service provider since part of their network is on 
our block list. You can also refer your provider to 
http://mail.live.com/mail/troubleshooting.aspx#errors.

That link leads to a definition of 550 SC-002 of "The mail server IP connecting 
to Outlook.com has exhibited namespace mining behavior."

How can I avoid this?

Original issue reported on code.google.com by ala...@gmail.com on 6 Apr 2014 at 5:54

Dovahkiin1991 / php-smtp-email-validation

Blacklisted by Hotmail but OK with Gmail/AOL #28