Best Free WordPress SMTP & Email Deliverability Plugins: Fix Not Sending Emails, PHP Mail Failures & Authentication (SPF, DKIM, DMARC)

One of the most persistent and frustrating problems WordPress site owners encounter is the “WordPress not sending emails” issue.

Whether it is a customer who never receives their WooCommerce order confirmation, a lead submission from your contact form that vanishes into thin air, or an administrator locked out of their dashboard because the password reset email never arrives, email deliverability failures can bring your business operations to an abrupt halt.

To permanently solve this, you need to understand why WordPress fails at sending emails out of the box, what a WordPress SMTP plugin actually does, and how modern email authentication ensures your messages land in the primary inbox rather than the spam folder.

How the Default WordPress Email System Works (And Why It Fails)

By default, whenever WordPress triggers an email—such as a user registration, a new comment alert, or a form submission—it calls an internal PHP function named wp_mail(). Under the hood, this function relies on your hosting server’s default mail agent via standard PHP mail().

This default workflow creates significant deliverability vulnerabilities for beginners:

1. Shared Hosting IP Reputation: Most entry-level WordPress sites reside on shared hosting. If another website on your shared IP server sends spam, the entire server IP gets blacklisted by major email providers like Gmail, Yahoo, and Microsoft Outlook.
2. Missing Cryptographic Authentication: The basic PHP mail() function sends plain, unauthenticated messages. It does not sign emails with cryptographic keys (DKIM) or verify sender authorization (SPF), causing modern recipient filters to reject them outright.
3. No Delivery Confirmation or Retry Logic: PHP mail() simply hands the message off to the server daemon. If the server fails to dispatch it, WordPress receives no error code, leaves no log entry, and makes no retry attempt.

What Is SMTP and How Does an SMTP Plugin Fix Deliverability?

SMTP stands for Simple Mail Transfer Protocol. It is the universal standard protocol used across the internet to transmit email messages securely between servers.

Instead of forcing your WordPress web server to act as a mail delivery agent (a task web servers are not optimized for), a WordPress SMTP plugin re-routes all outgoing wp_mail() traffic through a dedicated, authenticated email delivery service (such as SendGrid, Brevo, Mailgun, Amazon SES, Postmark, or Google Workspace / Microsoft 365).

Why Modern Email Authentication (SPF, DKIM, DMARC) Matters

When you send emails through a dedicated SMTP service, your domain is protected by three essential authentication records that you configure in your DNS settings:

• SPF (Sender Policy Framework): A public DNS TXT record that explicitly specifies which mail servers and IP addresses are authorized to send emails on behalf of your domain name.
• DKIM (DomainKeys Identified Mail): Adds an encrypted digital signature to the header of every outgoing email. The receiving mail server uses your public DNS key to verify that the email truly originated from your domain and was not tampered with in transit.
• DMARC (Domain-based Message Authentication, Reporting, and Conformance): A governance policy instructing receiving mail servers how to treat messages that fail SPF or DKIM checks (e.g., allow, quarantine to spam, or reject completely), while generating deliverability reports for your domain.

Critical Business Problems Caused by Broken WordPress Emails

When transactional emails fail to deliver, the repercussions impact sales, user trust, and administrative workflows:

• Lost Customer Inquiries: Potential clients fill out your contact form, but because notification emails fail, inquiries sit unanswered, costing you sales.
• WooCommerce Checkout Friction: Customers expect instant receipts and order tracking. Missing confirmation emails lead to anxious buyers, chargeback threats, and support ticket surges.
• Admin Lockouts: If your site experiences security lockout issues or you forget your credentials, missing password reset emails can leave you completely locked out of the WordPress dashboard.
• Broken User Registrations & Activations: Membership sites, online learning platforms (LMS), and community forums rely on automated activation links. Undelivered activation emails stall user growth immediately.

The Most Popular SMTP Mailer Services (And Where to Get Required Credentials)

WordPress SMTP plugins do not send emails on their own; they act as a bridge connecting your WordPress site to a reliable mailer service. Depending on the mailer you select, you will need either API Keys or standard SMTP Credentials:

Where to Find These Credentials

• If using a dedicated Transactional Mailer (Brevo, SendGrid, Mailgun): Log in to your mailer account dashboard, navigate to Settings > API Keys (or SMTP & API), and click Generate New Key. Copy this key into your WordPress SMTP plugin settings.
• If using Google Workspace / Gmail: Modern SMTP plugins use secure OAuth 2.0 so you do not have to expose your raw account password. You create a project in the Google Cloud Console, enable the Gmail API, generate an OAuth Client ID & Secret, and authorize the connection.
• If using Your Web Hosting Mail (cPanel / Webmail): In your cPanel dashboard, navigate to Email Accounts > Connect Devices (or Set Up Mail Client). Look for Outgoing Server (SMTP) details, which list your mail server address (e.g., mail.yourdomain.com), the secure SSL port (typically 465), and your full email address and password.

Here is an in-depth review of the best free WordPress SMTP and email deliverability plugins, comparing setup simplicity, background logging, fallback routing, and native mailer API support.

1. WP Mail SMTP by WPForms (Freemium)

Active on over 4 million WordPress sites, WP Mail SMTP by the WPForms/Awesome Motive team is the undisputed heavyweight in the email deliverability space. It solves default wp_mail() failures by reconfiguring outgoing email traffic through reliable SMTP protocols or direct API-based connections.

Using secure API endpoints (rather than standard SMTP ports) means emails bypass restrictive hosting environments where port 25, 465, or 587 might be blocked. With a streamlined Setup Wizard and direct OAuth 2.0 authentication for Google Workspace and Gmail, it makes professional email configuration accessible even to non-technical beginners.

Mailer Support & Core Mechanisms

• Free Native Mailer APIs: SendLayer, SMTP.com, Brevo (Sendinblue), Google Workspace / Gmail (via secure OAuth 2.0), SendGrid, Mailgun, Postmark, SparkPost, Elastic Email, and SMTP2GO.
• Pro-Exclusive Mailer APIs: Amazon SES (Simple Email Service), Microsoft 365 / Outlook (One-Click OAuth), and Zoho Mail.
• Universal Fallback: “Other SMTP” option allows manual configuration for any standard web host, cPanel, or third-party SMTP server (Host, Port, SSL/TLS, Username, Password).
• Sender Controls: Enforce a global “From Name” and “From Email” across all plugins, preventing third-party tools from sending unauthorized unauthenticated mail.

Key Features: Free vs. Pro Capabilities

Free Version Features

• Step-by-Step Setup Wizard: Walks users through selecting a mailer, retrieving API keys, and testing live email delivery.
• Email Testing Tool: Built-in test console sends a verification email to confirm authentication (SPF, DKIM, DMARC) and diagnose server connection handshake issues.
• Core API Integrations: Full access to Brevo, SendGrid, Mailgun, and Google OAuth without requiring paid licenses.

Pro Version Upgrades

• Email Logging & Resend Engine: Complete historical log of all outgoing emails with delivery status, open/click tracking, attachment storage, and one-click bulk resend capabilities.
• Backup Connections & Smart Conditional Routing: Automatically switch to a secondary backup mailer if the primary provider goes down, or route emails to different providers based on subject line, sender address, or source plugin.
• Instant Failure Alerts: Receive immediate notifications via Slack, Microsoft Teams, Discord, SMS (Twilio), or webhooks if an email fails to dispatch.
• Background Queue & Rate Limiting: Queues outgoing mail to prevent server slowdowns and restricts delivery rates to comply with provider throttle limits.

Pros and Cons

Final Verdict: Who Should Use It?

WP Mail SMTP is the best choice for general website owners, corporate blogs, and small businesses looking for an established, highly dependable plugin to fix email delivery using standard SMTP or major free-tier APIs like Brevo, SendGrid, or Google Workspace.

2. Easy WP SMTP (Freemium)

Maintained by the same core engineering organization behind WP Mail SMTP, Easy WP SMTP is designed as a streamlined, low-overhead alternative focused on straightforward configuration. It targets site owners who want to fix WordPress email deliverability without wading through complex multi-tab administrative panels.

While it shares the underlying reliability and stability of its sibling, Easy WP SMTP strips away clutter in the initial interface. It allows merchants, bloggers, and non-technical site managers to quickly route WordPress transactional emails through popular cloud mailers or custom server credentials.

Mailer Support & Core Mechanisms

• Free Mailer Integrations: SendLayer, Brevo (Sendinblue), Mailgun, SendGrid, Mailjet, SMTP.com, Postmark, SparkPost, and SMTP2GO.
• Pro-Exclusive Mailer Connections: Google Workspace / Gmail (1-click direct account authentication), Amazon SES, Microsoft 365 / Outlook, and Zoho Mail.
• Custom SMTP Server: Universal connection option allowing configuration of custom hostnames, SMTP ports (25, 465, 587), SSL/TLS security protocols, and authentication credentials.
• Debug Events Logging (Free): Unlike many alternatives that completely hide diagnostic tools behind paywalls, the free tier includes a debug events log that records failed transmission attempts and pinpointing error codes.

Key Features: Free vs. Pro Capabilities

Free Version Features

• Simplified Setup Wizard: Streamlined onboarding flow tailored to configure custom host SMTP or cloud API keys in minimal steps.
• Native Debug Events: Automatically logs failed outgoing messages and captures the originating plugin along with the server response code to diagnose broken forms or orders.
• Custom Headers & Fallbacks: Set explicit “From Email”, “From Name”, “Reply-To”, and BCC addresses across all outgoing WordPress messages.

Pro Version Upgrades

• Fast 1-Click Google/Gmail Authentication: Connects a Google Workspace or personal Gmail account without requiring the user to navigate the Google Cloud Console or configure custom API project credentials.
• Full Email Logging & Attachment Archiving: Searchable audit trail of all sent messages, open/click rate tracking, and one-click bulk resending of failed notifications.
• Backup Connections & Conditional Routing: Automated failover to a backup mailer if the primary provider encounters network downtime, plus rule-based routing to separate marketing and transactional traffic.
• Background Queue & Rate Throttling: Asynchronous email dispatching that offloads delivery tasks from page load processes to prevent front-end performance bottlenecks.

Pros and Cons

Final Verdict: Who Should Use It?

Easy WP SMTP is best suited for beginners, local business websites, and non-technical store managers who want a simplified, fuss-free setup to connect third-party mailers like Brevo, SendGrid, or custom hosting SMTP without navigating bloated administrative dashboards.

3. FluentSMTP (100% Free & Open Source)

Developed by WPManageNinja (the creators of Fluent Forms and FluentCRM) as an official contribution to WordPress Foundation’s “Five for the Future” initiative, FluentSMTP has disrupted the WordPress email deliverability ecosystem.

Unlike traditional freemium plugins that lock core functionality behind expensive paywalls, FluentSMTP is 100% free and open-source forever—with no pro version, no feature gates, no email capture walls, and zero upsell banners.

Built as a lightweight Vue.js single-page application (SPA), it connects directly via native REST APIs to every major cloud transactional mailer—including Amazon SES, Microsoft 365, and Google Workspace—without charging a single penny. It also includes full email logging, resend capabilities, multi-mailer fallback routing, and developer-friendly WP-CLI commands right out of the box.

Mailer Support & Core Mechanisms

• Free Native API Integrations (Zero Cost): Amazon SES (with optimized cURL-tunneling), Google Workspace / Gmail OAuth, Microsoft 365 / Outlook OAuth, SendGrid, Mailgun, Brevo (Sendinblue), Postmark, Cloudflare Email Sending, toSend, SparkPost, Netcore (Pepipost), Elastic Email, and SMTP2GO.
• Custom SMTP Server: Universal connection support for any standard web host, cPanel, or private SMTP server with custom ports and SSL/TLS encryption.
• Multi-Connection Routing: Connect unlimited email providers simultaneously. FluentSMTP can automatically route messages based on the “From Email” address (e.g., dispatching transactional receipts via Amazon SES and marketing notifications via SendGrid).
• Multi-Part MIME on the Fly: Automatically generates a plain-text alternative alongside HTML emails on the fly, significantly reducing spam filter flags.

Key Features & Technical Highlights

1. Unrestricted Native Features

• Zero Paywalls: Features commonly monetized by competitors—such as Amazon SES API integration, Microsoft 365 OAuth, and complete email logging—are completely free.
• Smart Fallback Connections: Automatically retries and dispatches failed messages using a designated backup connection if the primary mailer encounters network downtime.
• Dedicated Custom Database Table: Stores email logs in an independent custom table to prevent bloating standard wp_posts or wp_options tables, complete with auto-pruning rules.

2. Monitoring, Alerts & Developer Utilities

• Multi-Channel Real-Time Alerts: Instantly sends failure alerts via Telegram, Slack, Discord, or Pushover the moment an outgoing email fails to send.
• Automated Daily Health Monitoring: Performs automated daily connection health checks to identify expired OAuth tokens or revoked API keys before critical emails bounce.
• wp-config.php Constant Storage: Hardcode sensitive API keys and SMTP passwords directly inside wp-config.php for enterprise-level security.
• Comprehensive WP-CLI Commands: Manage and test mail connections directly from the server terminal (wp fluent-smtp test, wp fluent-smtp health, wp fluent-smtp stats, wp fluent-smtp prune-logs).

Pros and Cons

Final Verdict: Who Should Use It?

FluentSMTP is the undisputed best choice for developers, agency owners, WooCommerce merchants, and cost-conscious site owners who want an enterprise-grade, blazing-fast SMTP engine with built-in logging, backup connections, and native Amazon SES or Microsoft 365 support without ongoing subscription costs.

4. Post SMTP (Freemium)

Active on over 300,000 WordPress sites, Post SMTP is a diagnostic-first email deliverability engine originally engineered as the modern successor to the classic Postman SMTP. It stands out by combining enterprise-level diagnostic auditing with real-time remote monitoring.

Rather than treating email delivery as a silent background script, Post SMTP incorporates a built-in DNS Spam Score Checker (verifying SPF, DKIM, and DMARC records automatically), native browser alerts via a free Chrome extension, and a dedicated iOS and Android mobile app to monitor site health and resend failed transactional emails on the go.

Mailer Support & Core Mechanisms

• Free Mailer Integrations: Brevo (Sendinblue), Mailgun, SendGrid, Postmark, SparkPost, Mailjet, Elastic Email, Mandrill, Mailtrap, Cloudflare SMTP, Sweego, Emailit, Resend, MailerSend, and standard SMTP.
• Pro-Exclusive Mailer APIs: Microsoft 365 / Outlook (One-Click OAuth), Google Workspace / Gmail (One-Click OAuth), Amazon SES, and Zoho Mail.
• Custom SMTP Fallback: Configures any custom mail server with granular port controls, SSL/TLS certificates, and authentication modes.
• DNS Health Auditor: Evaluates your domain’s live DNS records directly from the WordPress dashboard to confirm SPF and DKIM signatures before you begin sending.

Key Features: Free vs. Pro Capabilities

Free Version Features

• Built-in Email Logging (Free): Unlike many competitors, Post SMTP includes functional email logs in its free version, allowing site managers to audit sent messages and diagnose delivery errors.
• DNS Spam Score & Authentication Audits: Checks domain DNS records for active SPF, DKIM, and DMARC configurations to diagnose inbox placement issues.
• Dedicated Mobile App & Chrome Extension: Connects to a companion mobile application and free Chrome extension to receive push notifications whenever an outgoing email fails.
• 3-Step Setup Wizard: Streamlined configuration wizard that tests outbound connectivity and firewall port restrictions before finalizing settings.

Pro Version Upgrades

• One-Click Gmail & Microsoft 365 Setup: Connects Google Workspace and Office 365 accounts via pre-configured API routing without requiring manual setup in developer consoles.
• Amazon SES & Zoho API Support: Adds direct API connectivity for low-cost Amazon SES sending and Zoho business mail.
• Automatic Failed Email Resending: Automatically schedules resubmission attempts when temporary server disconnects or recipient rate limits occur.
• Email Batching & Quota Scheduling: Configures outbound hourly, daily, or weekly delivery throttles to avoid triggering provider spam flags or exceeding daily limits.
• Centralized MainWP Integration: Syncs SMTP settings, email logs, and deliverability reports across multiple client sites from a single MainWP dashboard.

Pros and Cons

Final Verdict: Who Should Use It?

Post SMTP is an exceptional choice for freelancers, agencies, and store managers who want built-in email logging in the free version, live DNS authentication checks (SPF/DKIM/DMARC), and the convenience of mobile alerts and Chrome extension monitoring for client websites.

Best Free WordPress SMTP & Email Deliverability Plugins: Comparison Matrix

Here is a side-by-side comparison of the top WordPress SMTP and email deliverability plugins reviewed in this guide:

Final Thoughts: Which WordPress SMTP Plugin Should You Choose?

Fixing WordPress email delivery comes down to matching your technical workflow and preferred email service provider:

1. For zero-budget, enterprise-grade functionality with Amazon SES or Microsoft 365: Choose FluentSMTP. It is 100% free and open-source, offering unrestricted email logs, multi-mailer fallback routing, and native API connectivity that competing tools gate behind paid subscriptions.
2. For market-tested stability and seamless third-party plugin synergy: Choose WP Mail SMTP. It powers millions of sites, offers direct Google OAuth in its free version, and provides polished background queueing and failover routing in its Pro edition.
3. For built-in DNS health auditing and mobile-first delivery monitoring: Choose Post SMTP. Its free email logging, DNS spam score checker, and mobile app make tracking client site deliverability straightforward.
4. For non-technical site managers wanting a simple, fuss-free setup: Choose Easy WP SMTP to route outgoing mail through cloud providers like Brevo without navigating complicated dashboards.

Recommended Reading

To further enhance your WordPress site’s communication, security, and lead generation workflows, explore these related guides:

• Best Free WordPress Contact Form Builder Plugins (AI Forms, Payment Forms, Surveys & Quizzes) — Build high-converting, accessible forms that integrate seamlessly with your new SMTP delivery setup.
• Best Free WordPress Captcha Plugins: Cloudflare Turnstile, Google reCAPTCHA & hCaptcha for Bot Protection — Stop form spam, bot submissions, and malicious mail abuse before they trigger your SMTP sending limits.
• Best Free WordPress Email List Plugins to Build Your Audience — Grow your subscriber database with targeted opt-in forms, popups, and newsletter integrations.
• Best Free WordPress Security Plugins: Top Tools to Secure Your Site Without Slowing It Down — Protect your server IP reputation, block malicious login attempts, and harden your WordPress installation.