This covers information that we know about Hotmail, Outlook, Live.com and whatever domains Microsoft decides to register for their free email product in the future. Filtering decisions are based on a combination of sender reputation and email content.
This page does not cover filtering for other Microsoft email services, including Frontbridge and Exchange hosted products.
Hotmail does limit the amount of mail a sender can send based on the reputation of the sender. Senders with poor reputation may be limited to as few as 15,000 emails a day. Senders with good reputations sometimes see delivery problems, and may sometimes see Hotmail silently discard email they judge to be spam.
Hotmail has some information pages for senders on their Postmaster Website. On these pages they provide information for senders and other ISPs. They provide links to signup for their FBL and the SNDS program.
Homtail provides a self administered FBL that they call the JMRPP. Applications can be submitted on the JMRPP signup pages. To sign up Hotmail collects the following information:
Hotmail has a 2 step process to confirm that the FBL applicant has the authority to receive complaints about mail from those IPs. The first step is to confirm that the FBL address is authorized to receive the email. They do this by sending an email to abuse@ or postmaster@ the domain in the FBL example. For example, assume you’re using ISP@example.com for the FBL email address. You must have access to either abuse@ or email@example.com in order to confirm the request. The ISPs will allow you to choose which address they should send the confirmation to. Once the confirmation email is received, the link in the email must be clicked in order to move on to the next step in the FBL application process.
The second step is to electronically sign a Junk Mail Reporting Partner Program agreement. Hotmail will ask for the name and position of someone authorized to sign for the company, then send a link to the signature page to that person.
Hotmail does not provide a whitelist to senders.
Hotmail is rejecting mail based on DMARC records.
Hotmail does use Return Path Certified . Return Path Certified senders are given preferential treatment, delivering to the inbox with images enabled by default. Certified IPs also do not have the daily and hourly rate limits other senders do. Certified mail cannot guarantee inbox placement because user level preferences are always honored.
Hotmail provides web based support for senders who are having problems delivering to Hotmail.
Hotmail support pages
Hotmail also provides access to data about IP addresses through their SNDS (smart network data services) program. This lets authorized users see information about their sending IPs, including number of complaints and spam trap hits. This will also tell users if an IP is blocked by Hotmail.
Most of Hotmails spamfilters are built in-house and they do not use commercial spam filtering services in general.