I've been battling Outlook.com's spam filtering system for months with one particular domain that passes all authentication checks yet consistently lands in junk folders. The headers show perfect SPF, DKIM, and DMARC alignment:

Authentication-Results: 
  spf=pass (sender IP is 192.0.2.1)
  smtp.mailfrom=example.com; outlook.com;
  dkim=pass (signature was verified) header.d=example.com;outlook.com;
  dmarc=pass action=none header.from=example.com;

Beyond the standard authentication protocols, Outlook employs proprietary reputation algorithms. These consider factors like:

• Engagement patterns (how recipients interact with your emails)
• Volume spikes (sudden increases in sending volume)
• Content patterns (phrases commonly found in spam)

Microsoft provides the Smart Network Data Service (SNDS) for senders:

# Sample API request to check IP reputation
import requests

api_url = "https://snds.msft.net/api/v1/ip/192.0.2.1"
headers = {"Authorization": "Bearer YOUR_API_KEY"}

response = requests.get(api_url, headers=headers)
print(response.json())

Key metrics to monitor in SNDS:

• Filter rate (should be below 5%)
• Complaint rate (should be below 0.1%)
• Trap hits (should be zero)

Even with perfect technical setup, content can trigger filters. Try this HTML email sanitizer:

function sanitizeEmailContent(content) {
  // Remove hidden divs
  content = content.replace(/<div[^>]*style\s*=\s*["'][^"']*display\s*:\s*none[^"']*["'][^>]*>.*?<\/div>/gis, '');
  
  // Normalize font styles
  content = content.replace(/<span[^>]*style\s*=\s*["'][^"']*font-weight\s*:\s*bold[^"']*["'][^>]*>/gi, '<strong>');
  
  return content;
}

For direct troubleshooting, use:

1. Submit through Live.com Postmaster
2. Include full headers and message samples
3. Request specific feedback about your domain

Here's how to parse authentication results programmatically:

const headers = Received: from ...;

function parseAuthResults(headers) {
  const authRegex = /Authentication-Results:.+?(spf|dkim|dmarc)=(\w+)/gis;
  const matches = [...headers.matchAll(authRegex)];
  
  return matches.reduce((acc, match) => {
    acc[match[1]] = match[2];
    return acc;
  }, {});
}

console.log(parseAuthResults(headers));

When your emails pass all authentication checks (SPF, DKIM, DMARC) but still land in Outlook.com's spam folder, it indicates deeper deliverability issues beyond basic DNS configurations. The headers show:

Authentication-Results: 
    spf=pass (sender IP is XXX.XXX.XXX.XXX)
    smtp.mailfrom=EXAMPLE.COM; outlook.com;
    dkim=pass (signature was verified) header.d=EXAMPLE.COM;outlook.com;
    dmarc=pass action=none header.from=EXAMPLE.COM;

Create a diagnostic script to monitor deliverability:

#!/bin/bash
# Email Deliverability Tester
DOMAIN="example.com"
TEST_EMAIL="test@$DOMAIN"
RECIPIENT="your_account@outlook.com"

echo "Running full diagnostics for $DOMAIN..."
echo -e "Subject: Deliverability Test\nThis is a test email" | \
sendmail -f "$TEST_EMAIL" "$RECIPIENT"

# Check DNS records
echo "\nDNS Verification:"
dig TXT $DOMAIN +short
dig TXT _dmarc.$DOMAIN +short
dig TXT selector1._domainkey.$DOMAIN +short

Microsoft's filtering algorithms consider these additional factors:

• Sender reputation score (based on historical data)
• Engagement metrics (open rates, reply patterns)
• Content patterns matching known spam signatures

Implement feedback loops with Microsoft:

# Python snippet to process SNDS data
import requests

def check_snds_status(ip_address, api_key):
    url = f"https://sendersupport.olc.protection.outlook.com/snds/ipStatus.aspx?ip={ip_address}"
    headers = {"Authorization": f"Bearer {api_key}"}
    response = requests.get(url, headers=headers)
    return response.json()

# Example usage
snds_data = check_snds_status("XXX.XXX.XXX.XXX", "your_api_key")
print(f"Reputation score: {snds_data['ReputationScore']}")

For direct Microsoft support:

1. Submit through Outlook.com Sender Support
2. Register for Microsoft Postmaster Tools
3. Use the Microsoft Support Form

Check for these red flags in your emails:

// JavaScript content analyzer
const spamKeywords = [
    "limited time offer", 
    "click here",
    "dear customer",
    /!\$\d+\.\d{2}/,
    /% off/i
];

function analyzeContent(text) {
    return spamKeywords.some(pattern => 
        typeof pattern === 'string' 
            ? text.toLowerCase().includes(pattern)
            : pattern.test(text)
    );
}