In today’s email landscape, deliverability matters more than ever. Whether you’re a business or an individual, understanding email authentication—SPF, DKIM, and DMARC—can help ensure your emails reach their intended recipients rather than being flagged as spam.
This guide explores these critical email protocols and how they are supported by popular providers like iiNet, Microsoft 365 (M365), Gmail, Outlook.com, BigPond, and ProtonMail. We also include strategies to boost your deliverability further.
Email Authentication Basics
1. SPF (Sender Policy Framework)
What it does: SPF defines which mail servers can send emails on behalf of your domain.
How it works: When an email is sent, the recipient’s server checks your SPF record to confirm if the sending IP is authorized. If it’s not, the email may be marked as spam.
2. DKIM (DomainKeys Identified Mail)
What it does: DKIM adds a digital signature to each email, ensuring it hasn’t been tampered with during transit.
How it works: A cryptographic signature is added to your emails. The public key is stored in your DNS, and recipients can use it to verify authenticity.
3. DMARC (Domain-based Message Authentication, Reporting, and Conformance)
What it does: DMARC enforces SPF and DKIM policies, letting you decide what happens to emails that fail these checks. It also provides reports on email activity.
How it works: You can set DMARC policies to quarantine or reject unauthenticated emails, protecting your domain from spoofing.
Provider-Specific Support for SPF, DKIM, and DMARC
| Provider | SPF | DKIM | DMARC | Summary |
|---|---|---|---|---|
| iiNet | Supported | Not supported | Partially supported | Basic SPF and limited DMARC, but no DKIM. |
| M365 | Fully supported | Fully supported | Fully supported | Excellent for secure email authentication. |
| Gmail | Fully supported | Fully supported | Fully supported | Great for both individual and business use. |
| Outlook.com | Fully supported | Partially supported | Partially supported | Good for personal use, but limited DKIM support. |
| BigPond | Supported | Not supported | Partially supported | Basic support but not ideal for professional use. |
| ProtonMail | Fully supported | Fully supported | Fully supported | Ideal for secure, encrypted communications. |
Example Scenarios for Email Providers
1. iiNet
You add an SPF record for iiNet, but emails lack DKIM signing, limiting deliverability with some providers. A DMARC record can help monitor activity but can’t enforce full security.
2. M365
Using M365, you set up SPF, DKIM, and DMARC. Emails are fully authenticated, reducing spam risks and protecting against spoofing.
3. Gmail
With Google Workspace, SPF, DKIM, and DMARC ensure your emails are authenticated for excellent deliverability.
4. BigPond
Adding SPF works, but without DKIM, deliverability can suffer. DMARC monitoring is possible, but enforcement is limited.
Beyond SPF, DKIM, and DMARC: Advanced Deliverability Strategies
1. BIMI (Brand Indicators for Message Identification)
Display your logo in recipient inboxes to boost brand recognition and trust.
2. List Hygiene
Regularly clean your email list to remove inactive or unengaged recipients.
3. Sender Reputation Monitoring
Monitor your domain’s reputation using tools like Google Postmaster or Microsoft SNDS.
4. Engagement-Based Filtering
Focus on recipients who open and click your emails, improving overall engagement.
5. Throttling (Send Rate Management)
Control the rate of email sending to avoid triggering spam filters.
6. Feedback Loops (FBLs)
Track spam complaints and address issues causing them.
7. Dedicated IP Address
Use a dedicated IP for email sending to control reputation.
8. Email Content Optimization
Avoid spammy language and create relevant, high-quality content.
9. Warm-Up Process for New IPs or Domains
Gradually increase email sending volume to build a positive reputation.
10. Authentication-Results Header
Add email headers showing SPF, DKIM, and DMARC results for better trust.
Why Proper Email Authentication Matters
When you correctly use SPF, DKIM, and DMARC:
- ✅ Your emails avoid spam filters.
- ✅ You protect against spoofing and phishing.
- ✅ You gain insights into unauthorized use.
For businesses and individuals alike, these protocols ensure that emails are delivered securely and professionally.
Ready to Improve Your Email Deliverability?
Implementing SPF, DKIM, DMARC, and the strategies above is easier with expert guidance. At JTMi Services, we specialise in setting up secure, authenticated email systems tailored to your needs.
👉 Contact us today to boost your email success!