Email deliverability in iGaming does not fail for one reason. It fails because of ten small problems compounding. This checklist covers the 20 points that matter most for online casinos, sportsbooks, and poker platforms. Run through it quarterly, or after any significant deliverability drop.
Infrastructure (Points 1-5)
1. Dedicated IPs with Clean History
Check that you are sending from dedicated IPs, not shared pools. Verify each IP's history using tools like MXToolbox, Talos Intelligence, and Barracuda Reputation. A clean IP should show no listings on any major blacklist. If you are on a shared pool, your deliverability is at the mercy of every other sender on those IPs.
Action: Run a blacklist check on every sending IP. If any are listed, initiate delisting and investigate the cause.
2. SPF Records Are Correct and Under the Lookup Limit
Verify your SPF record includes all authorized sending sources and nothing else. Common issues for iGaming operators:
- Old ESP entries still in the record after migration
- Missing entries for platform-generated transactional emails
- Exceeding the 10 DNS lookup limit (causes SPF to fail entirely)
Action: Use an SPF validation tool to check syntax, lookup count, and authorized sources. Remove any entries for services you no longer use.
3. DKIM Signing Is Active and Valid
Confirm that every outbound email is DKIM-signed. Check that your DKIM keys are at least 2048 bits. Verify signatures by sending a test email and checking the Authentication-Results header.
Action: Send test emails to Gmail and check the "Show original" view for dkim=pass. If using multiple sending subdomains, verify DKIM for each one.
4. DMARC Policy Is at Quarantine or Reject
A p=none DMARC policy provides monitoring but no protection. For iGaming brands, where phishing and domain spoofing are common attack vectors, you should be at p=quarantine minimum, with a plan to reach p=reject.
Action: Check your DMARC record. If it is still p=none, review your DMARC reports for unauthorized senders, resolve any issues, and move to p=quarantine.
5. Reverse DNS (PTR) Records Match
Every sending IP should have a PTR record that resolves to a hostname under your control, and that hostname should resolve back to the IP. Mismatched or missing PTR records are a red flag for ISPs.
Action: Run dig -x [IP] for each sending IP. Verify the returned hostname resolves forward to the same IP.
Sending Practices (Points 6-10)
6. Transactional and Marketing Streams Are Separated
Transactional emails (password resets, withdrawal confirmations, KYC requests) must be on separate IPs and subdomains from marketing emails (bonuses, promotions, tournaments). If a promotional campaign damages your marketing IP reputation, your transactional delivery should be unaffected.
Action: Verify that transactional and marketing emails use different sending subdomains and different IP addresses.
7. Sending Volume Is Consistent
ISPs expect stable sending patterns. A casino that sends 50,000 emails on Tuesday and 500,000 on Friday looks suspicious. Spiky volume is one of the most common causes of throttling for iGaming operators, especially around major sporting events or new game launches.
Action: Review your sending volume over the past 30 days. If peaks exceed 3x your average daily volume, implement send throttling to spread large campaigns over multiple hours or days.
8. Bounce Handling Is Automated and Immediate
Hard bounces should be suppressed after the first occurrence. Soft bounces should trigger suppression after 3 consecutive failures. Check that your bounce processing is running in real time, not in a daily batch.
Action: Review your bounce suppression logs. Send a test to a known-invalid address and verify it is suppressed within minutes, not hours.
9. Feedback Loops Are Registered and Active
Register for ISP feedback loops wherever available. When a player marks your email as spam, you must suppress that address immediately. Not doing so will generate repeated complaints from the same user, which ISPs weight heavily.
Action: Verify FBL registration with Microsoft (JMRP/SNDS), Yahoo, and any other ISPs that offer them. Check that complaint suppressions are processed within minutes.
10. List Hygiene Runs on a Regular Schedule
iGaming databases degrade faster than most industries. Players use temporary email addresses, abandon accounts after bonus hunting, and change email providers frequently. Run email verification on your full list at least quarterly.
Action: Check when your last full list verification was performed. If it was more than 90 days ago, schedule one now. Expect to remove 5-10% of addresses each quarter.
Content and Engagement (Points 11-15)
11. Subject Lines Avoid Spam Trigger Patterns
Gambling subject lines are already under extra scrutiny. Do not make it worse with patterns that trigger spam filters:
- ALL CAPS words ("FREE SPINS" vs. "Free spins")
- Excessive punctuation ("Win BIG!!!" vs. "Win big")
- Deceptive phrasing ("You've won" when they have not)
- Excessive emoji usage
Action: Review your last 10 campaign subject lines. Flag any that use aggressive formatting and A/B test calmer alternatives.
12. Text-to-Image Ratio Is Healthy
Casino emails tend to be image-heavy (game thumbnails, promotional banners). ISPs penalize emails that are primarily images with little text. Aim for at least 60% text content by area.
Action: Open your last 5 campaigns with images disabled. If the email is unreadable without images, restructure the template.
13. Unsubscribe Mechanism Works and Is Visible
Every email must have a working unsubscribe link. It must process within 24 hours (regulatory requirement for MGA and UKGC licenses). Additionally, implement List-Unsubscribe headers so that ISPs can display their native unsubscribe buttons.
Action: Test your unsubscribe flow end-to-end. Click the link, confirm it works, and verify the address is suppressed within your system. Check that List-Unsubscribe and List-Unsubscribe-Post headers are present in your outbound emails.
14. Engagement-Based Segmentation Is Active
Do not send every campaign to your entire list. Segment by engagement level and send frequency accordingly:
- Active players (deposited in last 30 days): Full campaign frequency
- Lapsed players (30-90 days since last deposit): Reduced frequency, personalized re-engagement content
- Dormant players (90+ days): Very limited sends, dedicated re-engagement campaigns only
Action: Review your segmentation rules. If you are sending the same campaigns to all segments, implement tiered frequency immediately.
15. Re-engagement Campaigns Have a Sunset Policy
Players who do not respond to re-engagement attempts should be removed from your mailing list. A reasonable sunset policy for iGaming: if a player has not opened an email in 6 months and has not logged into the platform in 6 months, stop emailing them.
Action: Check if you have a sunset policy. If dormant addresses older than 12 months are still receiving emails, implement one now.
Monitoring and Analytics (Points 16-18)
16. Google Postmaster Tools Is Active and Reviewed Weekly
If you send to Gmail users (and you do), Postmaster Tools is non-negotiable. Check domain reputation, spam rate, and authentication results at least weekly. Set up alerts for any reputation drop to Low or any spam rate above 0.1%.
Action: Log into Google Postmaster Tools. If your domain is not verified, do it today. Review the last 30 days of data.
17. Inbox Placement Is Measured, Not Assumed
Delivery rate and inbox placement rate are different numbers. A 98% delivery rate means 98% of emails were accepted by the receiving server. But accepted emails can still land in spam. Use seed testing or panel-based tools to measure actual inbox placement at major ISPs.
Action: Run an inbox placement test across Gmail, Microsoft (Outlook/Hotmail), and Yahoo. If inbox placement is below 85% at any major ISP, investigate.
18. Blacklist Monitoring Is Automated
Do not discover a blacklisting when your open rates crash. Monitor your sending IPs and domains against all major blacklists continuously. Spamhaus, Barracuda, SORBS, and CBL are the most impactful for iGaming senders.
Action: Set up automated blacklist monitoring for every sending IP and domain. Verify that alerts are sent to a monitored inbox or Slack channel.
Compliance (Points 19-20)
19. Responsible Gambling Messaging Is Present
Every marketing email should include responsible gambling messaging appropriate to your licensing jurisdiction. For UKGC-licensed operators, this includes links to GamCare and BeGambleAware. For MGA-licensed operators, include your license number and a link to your responsible gambling page.
Beyond regulatory compliance, responsible gambling messaging signals legitimacy to ISPs. Legitimate operators include these disclosures. Spam senders do not.
Action: Check your email templates for responsible gambling content. Verify that the links work and point to current resources.
20. Self-Exclusion Integration Works
Self-excluded players must not receive marketing communications. Period. This is a licensing requirement under MGA, UKGC, and most other jurisdictions. Your email system must check against your self-exclusion database before every send.
Action: Add a test account to your self-exclusion list. Trigger a marketing campaign and verify that the test account does NOT receive the email. If it does, you have a compliance gap that needs immediate attention.
Running the Audit
Set a calendar reminder to run through this checklist every quarter. After any major event (ESP migration, IP change, significant volume increase, or a deliverability incident), run it immediately.
If multiple points on this list are failing, the compounding effect on your deliverability is likely worse than any single issue suggests. SMTPCloud provides deliverability audits for iGaming operators as part of its onboarding process and ongoing account management. If your internal team does not have dedicated email deliverability expertise, having a specialist review is worth the investment.
Good deliverability is not a project. It is an ongoing practice. Treat this checklist as a living document and update it as your email program grows.