If you send emails to Hotmail or Outlook users, getting your messages to the inbox is your top priority. To keep email delivery rates high and protect our network’s reputation, Mailbaby closely monitors feedback from Microsoft’s Smart Network Data Services (SNDS) and Junk Mail Reporting Program (JMRP).
The Changing Landscape of Hotmail Data
Over the years, Hotmail has changed how it reports junk mail. Today, specific details like the exact email content, spam trap hits, or individual recipient data are largely unavailable. However, Hotmail does still provide one critical piece of information: the specific domains that are getting marked as spam or experiencing delivery issues.
Because Hotmail and Outlook are incredibly quick to rate-limit or block senders based on IP reputation, Mailbaby takes the domain data Hotmail provides through SNDS at face value. We use this information to adapt our filters and maintain the best possible reputation for everyone on our network.
What is a P1 Sender Domain?
One specific metric Mailbaby targets is the P1 Sender domain. Hotmail defines this clearly: when a JMR (Junk Mail Reporting) complaint is received, Hotmail correlates and stores that complaint, attaching both the offending IP address and the P1 Sender domain.
Because this data directly reflects how Hotmail views your mail, Mailbaby incorporates these P1 listed domains into our filtering scores. If Hotmail is heavily flagging a domain, that will now impact how Mailbaby scores emails sent from that domain to Hotmail recipients.
How JMRP Listings Affect Your Delivery
To protect the shared IP reputation of all Interserver customers, Mailbaby enforces automated rules based on Hotmail’s JMRP data:
- Initial Listings: Any domain listed as a P1 Sender will automatically have a rule added to it. This applies a penalty score to outgoing mail addressed to Hotmail recipients, which may temporarily affect your delivery rates to Microsoft addresses.
- Consecutive Listings: If a domain is listed by Hotmail for two days in a row, Mailbaby will generate a much heavier, high-score flag for that domain. This strict approach is necessary to prevent a single problematic domain from damaging the reputation of the entire outbound IP.
- SRS Forwarded Emails: Domains utilizing Sender Rewriting Scheme (SRS) forwarding that appear in SNDS data or receive direct JMRP complaints face strict penalties. They will be specifically flagged under “SRS domains reports email as spam.” Because forwarded spam heavily damages IP reputation, these flagged domains will be extremely limited in the amount of email they are allowed to forward to Hotmail.
The Bigger Picture: Comprehensive Filtering
Hotmail SNDS data is just one piece of the puzzle. Mailbaby combines these domain lists with other critical data points, including bounce rates, feedback loop (FBL) complaints, and standard content scanning.
By taking immediate action on problematic domains and utilizing a layered approach to spam filtering, we help ensure a clean, highly reputable email environment. This proactive management means better inbox placement and more reliable email delivery for your business.
