Email Deliverability

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Email Authentication

Guides for configuring and troubleshooting SPF, DKIM, DMARC, and other email authentication protocols.

Email authentication is the foundation of deliverability. SPF, DKIM, and DMARC work together to prove your emails are legitimate and have not been tampered with. Without them, your messages fail provider checks and land in spam or get rejected outright. The articles below cover setup, troubleshooting, and advanced topics across all three protocols, plus supporting standards like MTA-STS, TLS, and PTR records.

For a comprehensive overview, see our Email Authentication Guide.

SPF Fail, Softfail, and Hardfail Explained

Understanding SPF authentication results: fail, softfail, hardfail, neutral, and pass. Learn what each result means and how to fix SPF failures.

SPF Multiple Records: Why You Can Only Have One and How to Fix It

Learn why having multiple SPF records breaks email authentication, how to detect this common mistake, and how to merge multiple SPF records into one.

SPF Softfail vs Hardfail: Understanding SPF Results and When to Use Each

Learn the difference between SPF softfail (~all) and hardfail (-all), plus other SPF qualifiers like neutral and permerror, and when to use each in your SPF record.

SPF Too Many DNS Lookups: How to Fix the 10 Lookup Limit

SPF records have a 10 DNS lookup limit. Learn what counts as a lookup, how to diagnose permerror, and strategies to flatten or optimize your SPF record.

SPF vs DKIM vs DMARC: What's the Difference?

SPF, DKIM, and DMARC work together to authenticate your email. Learn what each does, how they complement each other, and why you need all three.

DKIM Fail: Troubleshooting DKIM Authentication Errors

Your emails are failing DKIM checks. Learn what causes DKIM failures, from missing records to signature verification errors, and how to fix them.

DKIM Key Length: Choosing Between 1024-bit and 2048-bit Keys

Learn about DKIM key lengths, why 2048-bit keys are recommended, how to check your current key size, and how to rotate to stronger keys.

DKIM Errors: Troubleshooting Permerror and Temperror

Fix common DKIM errors including permerror, temperror, body hash verification failures, and signature validation problems with step-by-step troubleshooting.

DMARC Alignment Explained: SPF and DKIM Alignment Requirements

Understand how DMARC alignment works, the difference between strict and relaxed alignment for SPF and DKIM, and how to fix alignment failures.

DMARC p=none Explained: What It Means and When to Move Beyond It

Understand what DMARC p=none policy means, why it's a starting point but not a destination, and how to transition to p=quarantine or p=reject.

DMARC Fail: Troubleshooting DMARC Authentication Failures

Your emails are failing DMARC checks. Learn what causes DMARC failures, how to diagnose alignment issues, and how to fix your SPF and DKIM configuration.

554 5.7.5 Permanent Error Evaluating DMARC Policy: How to Fix It

Getting '554 5.7.5 permanent error evaluating DMARC policy' bounces? Learn what causes this error and how to fix your DMARC, SPF, and DKIM configuration.

Email Authentication Failed: How to Fix SPF, DKIM, and DMARC Failures

Understand why email authentication fails and learn how to diagnose and fix SPF, DKIM, and DMARC authentication errors to improve your email deliverability.

Mailgun DMARC Setup: Configure DMARC for Mailgun Email

Step-by-step guide to setting up DMARC when using Mailgun. Configure SPF, DKIM, and DMARC alignment so your Mailgun emails pass authentication checks.

SPF Include Mechanism Explained: How to Authorise Multiple Senders

Understand how the SPF include mechanism works, how to add multiple email senders to your SPF record, and how to avoid the 10-lookup limit.

How to Set Up SPF, DKIM, and DMARC for Google Workspace

Step-by-step guide to configuring SPF, DKIM, and DMARC for Google Workspace. Fix authentication issues and improve deliverability for your business email.

10 Email Authentication Mistakes That Kill Deliverability

Common email authentication mistakes that damage deliverability. Learn how to avoid SPF, DKIM, and DMARC configuration errors that send your emails to spam.

Why Email Forwarding Breaks SPF (And How DKIM Saves You)

Email forwarding breaks SPF authentication because the sending IP changes. Learn why this happens, how DKIM and ARC solve the problem, and what to configure.

DNS Propagation and Email: Why Changes Take Time and What Can Go Wrong

Understand how DNS propagation affects email deliverability. Learn why SPF, DKIM, and DMARC changes take time to take effect and how to avoid downtime.

TLS Email Encryption: What It Is and Why Email Providers Require It

Understand TLS encryption for email, how STARTTLS works, why providers require it, and how to verify your email is being sent over encrypted connections.

MTA-STS Explained: How to Enforce TLS Encryption for Your Email

MTA-STS (Mail Transfer Agent Strict Transport Security) enforces TLS encryption for your domain's incoming email. Learn what it is, how to set it up, and why it matters.

DKIM Key Rotation: Why, When, and How to Rotate Your DKIM Keys

Learn why DKIM key rotation matters, how often to rotate keys, and step-by-step instructions for rotating DKIM keys without breaking email authentication.

How to Read DMARC Aggregate Reports (RUA): A Practical Guide

Learn how to read and interpret DMARC aggregate reports (RUA). Understand the XML format, identify authentication failures, and use reports to improve email deliverability.

DMARC Forensic Reports (RUF): What They Are and Why Most Providers Don't Send Them

Understand DMARC forensic reports (RUF), how they differ from aggregate reports (RUA), why most providers don't send them, and what alternatives exist.

DMARC Quarantine/Reject Policy Not Enabled: What It Means and How to Fix It

Seeing 'DMARC quarantine/reject policy not enabled' in a security audit? Learn what this warning means, why it matters, and how to safely enable DMARC enforcement.

SPF Record Too Long? How to Flatten and Fix It

Your SPF record exceeds the 10-lookup limit or the 255-character DNS limit. Learn how SPF flattening works and other strategies to fix an SPF record that's too long.

PTR Records and Email: Why Reverse DNS Matters for Deliverability

Understand PTR records (reverse DNS) and why they matter for email deliverability. Learn how to check and configure PTR records for your sending IP.

Managing Email Deliverability Across Multiple ESPs

Using multiple email service providers? Learn how to manage SPF records, avoid authentication conflicts, and maintain deliverability when sending from multiple platforms.