Why is hotmail Blocking/Junking my mail?

Because of Hotmail's extremely aggressive spam protection policies, senders may find valid emails being sent directly to recipient's junk folder or being blocked outright.

Below is the standard response send from Hotmail support regarding this issue. The only way to remove yourself from Hotmail's block list is to work with the steps listed below:

We have identified that messages from your IP are being
filtered based on the recommendations of the SmartScreen filter.
SmartScreen is the spam filtering technology developed and operated by
Microsoft. SmartScreen is built around the technology of machine learning.
SmartScreen's filters are trained to recognize what is spam and what
isn't spam. In short, we filter incoming emails that look like spam. I am
not able to go into any specific details about what these filters
specifically entail, as this would render them useless.  
Hotmail/Windows Live Mail limits the number of e-mail messages a
particular IP can send within a time period. Based on an IP's reputation
(built based on various data sources) it is allotted an allowed sending
limit per unit of time. When an IP (sender) exceeds its allowed limit, any
further SMTP commands from the IP will receive the SMTP error code 421
from Hotmail/Windows Live Mail and the connection terminated.
Please confirm that your emails comply with MSN Hotmail's technical
standards. This information can be found at:
You may also be able to find additional information on common
delivery questions at the Hotmail Postmaster Site found at
Hotmail has created the Smart Network Data Services program. This is a
service that helps legitimate email senders work with their customers
and partners to reduce spam originating from their IP.
http://postmaster.msn.com/snds/. This program allows a sender to
monitor the 'health' of their IPs.
Monitor user complaints. Hotmail also has a sender complaint feedback
loop program Junk Email Reporting Program (JMRP). Enrollment in this,
free of charge, program will benefit you as a sender as it will keep your
e-mail lists updated and populated with interested MSN Hotmail
Customers. Participation in this program will remove those MSN Hotmail
Customers who do not want to receive e-mails from your company. If you are
interested in joining this program please visit
While using the SNDS tool, enrollment in the JMRP or having your IPs
registered with Sender ID will not allow emails from your mail servers to
bypass our filters, these are in place to help legitimate companies
deliver their emails to Hotmail Customers.
SenderScore Certified Mail Program. Many legitimate mailers and
marketers have qualified and joined this "white listing" program to improve
mail deliverability and decrease email from being filtered to the Junk
E-mail Folder. Sender Score is a third party program, administered by
Return Path. Sender Score (www.senderscorecertified.com) is the only White
Listing service to which we subscribe.  
Below are some links which show the reputation results of your IP:  x.x.x.x
Sender Score: 
Trusted Source: 
We would recommend working with both Sender Score and Trusted Source in order to build your reputation. 
Hotmail has created a group of programs to help avoid future issues I would strongly 
suggest enrolling-in or implementing these if you have not already.
1. Segment your mailing infrastructure by IP. Marketing e-mail,
transactional corporate, "forward to a friend" e-mail and signup e-mails
should be sent from different IP's. This will help to identify what types of
messages are being flagged by Hotmail customers.
 2. Strengthen the sign up process. Confirm that you are using a
double-opt-in sign up process. This will not help in removing existing Hotmail
customers from your e-mail lists but it will confirm the authenticity
of those who sign-up on for your e-mail campaigns and newsletters.
3. If you have any feedback loops setup with other ISPs you should look
for trends to try and determine possible causes - a new data source?
New advertisement? Maybe folks signing up don't recognize the mail?
4. Clearly mark your e-mails so that Hotmail customers are able to
quickly and easily identify that they requested e-mails from your service.
5. Do some analysis on the data regarding complaints - look at Hotmail
customers who have never clicked, opened, responded or bounced in any
way. These poor performers could contain many bad addresses.
6. Clean up your lists. Remove those who do not want to receive the
emails. Make the unsubscribe process more visible.
7. Enroll in the Sender Score program. This is the only Whitelist which
Hotmail uses. It is owned and operated by Return Path. You can find
information about this program at http://www.senderscorecertified.com.
8. Please visit http://www.senderbase.org or http://openrbl.org to
verify that your IP is not being targeted by any 3rd party block lists.
The troubleshooting steps in this email are recommendations only,
Microsoft makes no guarantees that following these steps will guarantee
deliverability to MSN, Hotmail, or Live.com customers.
Windows Live Hotmail Domain Support


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