Looking at your email headers, I spotted an immediate red flag in Yahoo's authentication report:

Authentication-Results: mta1035.mail.sk1.yahoo.com from=example.com; 
domainkeys=pass (ok); from=example.com; dkim=permerror (bad sig)

This indicates your DKIM signature is failing validation, though DomainKeys is passing. The inconsistency between authentication methods triggers spam filters.

For proper email authentication, you need these three DNS records properly configured:

; SPF Record
polluxapp.com. IN TXT "v=spf1 ip4:208.115.108.162 include:_spf.google.com ~all"

; DKIM Record (2048-bit recommended)
mail._domainkey.polluxapp.com. IN TXT "v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG...AQAB"

; DMARC Record
_dmarc.polluxapp.com. IN TXT "v=DMARC1; p=none; rua=mailto:postmaster@polluxapp.com"

Your sending IP 208.115.108.162 must have matching forward/reverse DNS:

$ host 208.115.108.162
162.108.115.208.in-addr.arpa domain name pointer gemini.polluxapp.com.

$ host gemini.polluxapp.com
gemini.polluxapp.com has address 208.115.108.162

Mismatches here are automatic spam flags for AOL/Hotmail.

Subject lines like "Shift License For James Xavier" contain multiple spam triggers:

• Capitalized names (James Xavier)
• License/key terminology
• Lack of recipient personalization

Better alternative:

Subject: Your PolluxApp license confirmation #AX-78392

Compare your From header and Return-Path:

From: "Shift Licensing" 
Return-Path: <bounces@polluxapp.com>

These should match exactly. Use consistent subdomains:

From: licensing@notifications.polluxapp.com
Return-Path: licensing@notifications.polluxapp.com  

Use this Python script to validate your setup:

import dkim
import dns.resolver

def verify_dkim(email_file):
    with open(email_file, 'rb') as f:
        message = f.read()
    return dkim.verify(message)

def check_spf(domain, ip):
    answers = dns.resolver.resolve(domain, 'TXT')
    spf_record = [r.to_text() for r in answers if 'v=spf1' in r.to_text()]
    # SPF validation logic here...
    return spf_match

Check your sending IP at:

• https://mxtoolbox.com/blacklists.aspx
• https://www.spamhaus.org/lookup/

Even with perfect authentication, poor IP reputation will land you in spam folders.

1. Match From/Return-Path domains exactly
2. Use 2048-bit DKIM keys (no 1024-bit)
3. Implement DMARC reporting
4. Maintain consistent reverse DNS
5. Warm up new IPs gradually

Remember that Yahoo/Hotmail/AOL apply stricter filters than Gmail. What passes at Google may still trigger spam filters elsewhere.

---

Your authentication setup appears technically correct when examining the headers:

Authentication-Results: 
  mta1035.mail.sk1.yahoo.com from=example.com; 
  domainkeys=pass (ok); 
  from=example.com; 
  dkim=permerror (bad sig)

The Yahoo header reveals a critical DKIM verification failure despite proper configuration. This often occurs when:

• The selector (s=mail) doesn't match DNS records
• Clock skew between servers exceeds tolerance
• Header fields are modified in transit

Notice the Hotmail header shows:

X-AUTH-Result: NONE
X-SID-PRA: james@gemini.example.com

This indicates SenderID validation failed. Implement Sender Policy Framework (SPF) v=spf1 records with proper alignment:

v=spf1 ip4:208.115.108.162 include:_spf.google.com ~all

AOL's headers show successful DKIM validation but still filtered:

X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d227.1 ; 
domain : gemini.example.com DKIM : pass

This suggests content triggering their filters. Check for:

• HTML/CSS ratio exceeding 30%
• Link density above industry standards
• Trigger words ("license", "shift") in subject lines

For programmatic email sending, use this Python validation template:

import dkim
import DNS

def verify_dkim(email):
    try:
        d = dkim.DKIM(email)
        return d.verify()
    except:
        return False

def check_spf(ip, domain):
    query = f"v=spf1 ip4:{ip} include:{domain} -all"
    return DNS.dnslookup(query, 'TXT')

Your sending IP 208.115.108.162 shows in Yahoo's filtered bulk list:

X-YahooFilteredBulk: 208.115.108.162

Check blacklists with this API call:

import requests
def check_blacklist(ip):
    bls = ['zen.spamhaus.org','bl.spamcop.net']
    return {bl:requests.get(f'https://{bl}/query?ip={ip}').status_code for bl in bls}

Reconstruct your headers to avoid these common pitfalls:

Received: from [127.0.0.1] (localhost [127.0.0.1])
    # Replace with actual public hostname
X-Mailer: Unknown (No Version)  
    # Specify your MTA version

When establishing new sending infrastructure:

# Week 1: 50 emails/day to engaged users
# Week 2: 100 emails/day with 40%+ open rate
# Week 3: Scale 20% daily if complaint rate <0.1%