Email Deliverability
Understand what affects whether your emails reach the inbox—and how to fix it.
Email deliverability is the ability to successfully deliver emails to recipients' inboxes. Poor deliverability means your emails end up in spam folders—or worse, get rejected entirely.
Why Deliverability Matters
Your sender reputation is like a credit score for email. Mailbox providers like Gmail, Yahoo, and Microsoft track:
- Authentication results — Do your emails pass SPF, DKIM, and DMARC?
- Engagement metrics — Do recipients open, click, or mark as spam?
- Complaint rates — How often do users report your emails as spam?
- Bounce rates — Are you sending to invalid addresses?
- Sending patterns — Are your volumes consistent or erratic?
2024 Sender Requirements
Google and Yahoo now require bulk senders (5,000+ emails/day) to have proper SPF, DKIM, and DMARC authentication. Non-compliant senders face delivery failures and rejections.
The Email Authentication Stack
Modern email authentication relies on three complementary protocols working together:
| Protocol | Purpose | Protects Against |
|---|---|---|
| SPF | Authorizes sending servers | Unauthorized servers sending as you |
| DKIM | Cryptographically signs messages | Message tampering in transit |
| DMARC | Policy enforcement & reporting | Domain spoofing & phishing |
How Mailbox Providers Score You
Each major mailbox provider maintains its own reputation system:
Google Gmail
Uses machine learning to evaluate sender reputation. Factors include authentication, user engagement, and spam reports.
Tool: Google Postmaster Tools
Microsoft Outlook/365
Maintains the Smart Network Data Services (SNDS) for reputation monitoring. Strong emphasis on authentication.
Tool: SNDS Portal
Yahoo Mail
Part of the Yahoo/AOL/Verizon family. Requires authentication and has strict complaint rate thresholds.
Tool: Complaint Feedback Loop
Improving Your Deliverability
Implement Full Authentication
Set up SPF, DKIM, and DMARC for all sending domains. Aim for a DMARC policy of p=reject.
Monitor Your Reputation
Use postmaster tools from Google, Microsoft, and Yahoo to track your sender reputation.
Maintain Clean Lists
Remove bounces and unsubscribes promptly. High bounce rates damage your reputation.
Enable TLS Encryption
Use MTA-STS to enforce encrypted connections for inbound mail.
Next Steps
Ready to improve your email deliverability? Start with these guides: