Due to Hotmail's very aggressive spam policy, you will have to work with the hotmail SmartScreen filter and follow official guidelines provided by the standard Hotmail email regarding this.
SmartScreen is the spam filtering technology developed and operated by Microsoft. SmartScreen is built around the technology of machine learning. Its filters are trained to recognize what is spam and what isn't spam. In short, we filter incoming emails that look like spam. Hotmail/Outlook 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.
Please confirm that your emails comply with MSN Hotmail's technical standards. This information can be found at: http://postmaster.live.com/Guidelines.aspx.
Find additional information at:
- Smart Network Data Services program that helps legitimate email senders work with their customers and partners to reduce spam originating from their IP — http://postmaster.msn.com/snds/
- Hotmail also has a sender complaint feedback loop program Junk Email Reporting Program (JMRP). 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 https://support.microsoft.com/en-us/search?query=Junk%20Email%20Reporting%20Program
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.
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.
Bellow are some services which display the reputation results of your IP:
NOTE: We would recommend using both Sender Score and Trusted Source in order to build your reputation.
- 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.
- 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.
- 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?
- Clearly mark your e-mails. This helps Hotmail customers to quickly and easily identify that they requested e-mails from your service.
- 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.
- Clean up your lists. Remove those who do not want to receive the emails. Make the unsubscribe process more visible.
- 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.
- 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 listed above are recommendations only, Microsoft makes no guarantees that following these steps will guarantee deliverability to MSN, Hotmail, or Outlook.com customers.