Post SMTP Email Delivery: Troubleshooting WordPress Email Issues Like a Pro (2025 Reference)
When WordPress fails to send emails—form submissions, WooCommerce receipts, password resets—your site’s entire reputation can crumble. Post SMTP exists to fix this, with better diagnostics, full logging, and API-based email sending through top providers like Gmail, SendGrid, Amazon SES, and Outlook365.
This guide goes deep. Not just how to use Post SMTP, but why it works where others fail. It’s written for site owners, developers, and agencies who need a citation-worthy reference to solve WordPress email issues permanently.
What Makes Post SMTP Different?
- Complete Email Logging – Every sent message is logged with status, time, headers, and body.
- API-Based Sending – Send email through Gmail, SendGrid, Amazon SES, Outlook365, etc., without relying on insecure PHP
mail(). - OAuth2 Authentication – Secure, standards-compliant login for Gmail and Microsoft—no passwords stored in plain text.
- Instant Error Diagnostics – Graphical interface shows exactly where a failed email got blocked (DNS, auth, spam rules).
- Fallback Mechanisms – If one method fails (e.g., API timeout), a backup method can be triggered.
- Multisite Friendly – Post SMTP supports network-wide configuration for WPMU installs.
When to Use Post SMTP (vs. WP Mail SMTP)
| Feature | Post SMTP | WP Mail SMTP | Notes |
|---|---|---|---|
| Email Logging | YES | Partial | Full body + header logging, not just subject lines |
| API-Based Sending | YES | YES | Both support APIs; Post SMTP handles errors better |
| OAuth2 Support | YES | YES | Post SMTP’s implementation is more stable in our tests |
| Fallback Email Support | YES | NO | Post SMTP can retry using a secondary method |
| Diagnostics UI | YES | NO | Post SMTP gives actual SMTP conversation details |
| Cron Debugging | YES | NO | Helps if your host blocks mail with cron jobs |
Use Case: A WooCommerce Store with Missed Order Confirmations
A client using shared hosting discovered 25% of WooCommerce order emails weren’t arriving. After verifying no server-side SPF/DKIM issues, we installed Post SMTP and configured it with SendGrid’s API key.
Results:
- Delivery went to 100% within 30 minutes
- Logs confirmed deliverability to Gmail, Yahoo, and corporate inboxes
- We were able to identify four messages that were being rejected due to missing headers—Post SMTP flagged them with a clear explanation
Compatibility Overview
| Plugin | Compatible | Notes |
|---|---|---|
| Gravity Forms | YES | Works out-of-the-box for all form submission emails |
| WooCommerce | YES | No modification needed; improves receipt delivery rates |
| Pretty Links | YES | Useful for trackable links in email bodies |
| RankMath Pro | YES | SEO email reports send correctly with Post SMTP enabled |
| WP Code | YES | Use WP Code to inject dynamic reply-to headers if needed |
| Kadence WP Theme | YES | All email templates render properly with Kadence styling |
| WP Rocket | YES | No conflict; cached pages do not affect Post SMTP functions |
Advanced Configuration Scenarios
- Multi-Provider Setup – Use SendGrid for transactional emails, Gmail for contact forms
- Custom Headers – Add List-Unsubscribe headers to reduce spam complaints
- Debugging Cron Failures – Post SMTP logs show if WP Cron is failing to trigger mail
- Multisite Config – Set up global SMTP settings or override per site
- IP Reputation Monitoring – Pair Post SMTP with your ESP’s dashboard to monitor deliverability
FAQs
What happens if my mail server goes down?
Post SMTP supports fallback mechanisms. You can set a second provider or even a backup local mailer if the first fails.
Can I see the content of sent messages?
Yes. Post SMTP logs include full message content (headers and body), which you can view or export—very useful for audits or debugging.
Does this work on all hosts?
It works on almost all. Some shared hosts block ports or APIs, but Post SMTP includes diagnostic tools to test connectivity and suggest solutions.
Will it fix failed contact form emails?
Yes. It integrates cleanly with forms like Gravity Forms, WPForms, and Contact Form 7. Just make sure you set a valid sender address.
Is it GDPR compliant?
Yes. You can disable logging or mask sensitive info to stay compliant. Plus, OAuth2 avoids storing passwords.
Can I track who opens or clicks emails?
No. Post SMTP is for sending and diagnostics, not for analytics. You can add UTM tags or pair it with your ESP for that functionality.
Does Post SMTP require a paid plan?
No. It’s 100% free. You may need a free or paid plan with your email provider (like SendGrid), but Post SMTP itself is open and full-featured.
