Hotmail

Filtering decisions are based on a combination of sender reputation and email content.

Delivering to Hotmail
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 20,000 emails a day. Senders with good reputations sometimes see delivery problems, and may sometimes see Hotmail silently discard email they judge to be spam.

Postmaster pages
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.

Feedback loop
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:
 * Contact information for an individual responsible for the FBL
 * Corporate contact information
 * An email address for the FBL email
 * The IP addresses covered by the FBL

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,

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.

Whitelist
Hotmail does not provide a whitelist to senders.

Certification Services
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.

Support for Senders
Hotmail provides web based support for senders who are having problems delivering to Hotmail.

Hotmail support pages

Known spamfilters
Most of Hotmails spamfilters are built in-house and they do not use commercial spam filtering services in general.