WordPress sends emails for password resets, new user registrations, purchase confirmations, and plugin notifications. But WordPress’s default email delivery method — PHP’s mail() function — is unreliable. Emails sent with PHP mail() are frequently flagged as spam or silently dropped by email providers. For a plugin business, unreliable email delivery means lost customers and missed opportunities.
This guide covers how to configure reliable email delivery for WordPress, from basic SMTP setup to advanced services like Amazon SES and Postmark.
Why PHP Mail() Fails
PHP’s mail() function sends emails directly from your web server without authentication, proper headers, or DKIM signing. Email providers like Gmail, Outlook, and Yahoo treat such emails as suspicious and often deliver them to spam folders or reject them entirely. For business-critical emails like purchase receipts and license keys, this is unacceptable.
Shared hosting servers are particularly problematic because your IP address is shared with hundreds of other sites — many of which may be sending spam. A single spammer on your hosting provider can get the entire IP range blacklisted, affecting your email deliverability.
SMTP Plugin Setup
The simplest fix is to use an SMTP plugin that routes WordPress emails through a proper email service. WP Mail SMTP is the most popular option, supporting Mailgun, SendGrid, Postmark, Amazon SES, and standard SMTP servers. Configure your email service credentials in the plugin, and it handles the rest — proper authentication, headers, and encryption.
Other SMTP plugins include Easy WP SMTP, Post SMTP, and FluentSMTP. Most support the same email services. Choose the one with the best interface and support for your specific email provider.
Amazon SES
Amazon Simple Email Service (SES) is a cost-effective option for high-volume WordPress email sending. SES charges around $0.10 per 1,000 emails, making it significantly cheaper than dedicated email services for sites sending thousands of emails monthly. SES requires verification of your sending domain and may need a support request to increase your sending limits from the default sandbox mode.
SES integrates with WordPress through SMTP plugins or the SES-specific WP Mail SMTP Amazon SES integration. Configure your AWS credentials and region in the plugin, and WordPress emails are routed through SES’s reliable infrastructure.
Postmark
Postmark is a premium email delivery service focused on transactional emails — exactly what WordPress sends. It offers the highest deliverability rates in the industry, with detailed analytics showing delivery status, opens, and bounces. Postmark costs $15/month for 10,000 emails plus $1.50 per additional 1,000 emails.
Postmark’s WordPress integration is straightforward through SMTP plugins. Create a Server in Postmark, generate an API token, configure it in your SMTP plugin, and verify your sending domain. Postmark automatically handles DKIM signing, SPF records, and bounce processing.
Email Testing and Monitoring
After configuring email delivery, test that everything works. Most SMTP plugins include a test email feature. Send a test to an address you control and verify it arrives in the inbox, not spam. Check the email headers to confirm DKIM, SPF, and DMARC authentication passed.
Set up email monitoring to track delivery issues. Services like Postmark and SendGrid provide bounce and complaint notifications. Monitor your email sending reputation and investigate any sudden drops in deliverability.
The Bottom Line
Reliable email delivery is essential for any WordPress business. Never rely on PHP’s mail() function for transactional emails. Use an SMTP plugin with a proper email service — Amazon SES for high volume on a budget, Postmark for the best deliverability, or a service like SendGrid or Mailgun as a middle ground. The configuration takes 30 minutes and ensures your emails reach their intended recipients.