MagicWP.io

Magic API Email replaces the default WordPress email system (<code>wp_mail()</code>) with a direct API connection to your chosen transactional email provider. No SMTP configuration needed — just paste your API key and you’re ready to go.
Supported Providers:
<ul>
<li><a href="https://resend.com" rel="nofollow ugc">Resend</a> — Modern email API for developers</li>
<li><a href="https://mailgun.com" rel="nofollow ugc">Mailgun</a> — Reliable transactional email</li>
<li><a href="https://postmarkapp.com" rel="nofollow ugc">Postmark</a> — Fast, deliverable transactional email</li>
<li><a href="https://mailtrap.io" rel="nofollow ugc">Mailtrap</a> — Email delivery platform with sandbox testing</li>
<li><a href="https://useplunk.com" rel="nofollow ugc">Plunk</a> — Email API for developers</li>
</ul>
Features:
<ul>
<li>Per-provider settings — API key, From Email, and From Name are stored independently for each provider. Switching providers never overwrites another provider’s credentials.</li>
<li>Test email — Send a test email directly from the settings page to verify your configuration.</li>
<li>Secure — All inputs are sanitized and validated. API keys are stored as password fields.</li>
<li>Lightweight — No dependencies, no bloat. Three focused class files.</li>
<li>Developer-friendly — Falls back to default <code>wp_mail()</code> if no API key is configured.</li>
</ul>
<h3>External services</h3>
This plugin acts as a bridge between your WordPress site and your chosen transactional email provider. By design, instead of sending emails via standard <code>wp_mail()</code>, this plugin sends the content of your outgoing emails via an HTTPS API request to the provider you select in the settings.
Depending on your configuration, the plugin connects to one of the following APIs: 
* Resend (api.resend.com) – <a href="https://resend.com/terms" rel="nofollow ugc">Terms of Service</a> | <a href="https://resend.com/privacy" rel="nofollow ugc">Privacy Policy</a> 
* Mailgun (api.mailgun.net) – <a href="https://www.mailgun.com/terms" rel="nofollow ugc">Terms of Service</a> | <a href="https://www.mailgun.com/privacy" rel="nofollow ugc">Privacy Policy</a> 
* Postmark (api.postmarkapp.com) – <a href="https://postmarkapp.com/terms-of-service" rel="nofollow ugc">Terms of Service</a> | <a href="https://postmarkapp.com/privacy-policy" rel="nofollow ugc">Privacy Policy</a> 
* Mailtrap (api.mailtrap.io) – <a href="https://mailtrap.io/terms" rel="nofollow ugc">Terms of Service</a> | <a href="https://mailtrap.io/privacy-policy" rel="nofollow ugc">Privacy Policy</a> 
* Plunk (api.useplunk.com) – <a href="https://useplunk.com/terms" rel="nofollow ugc">Terms of Service</a> | <a href="https://useplunk.com/privacy" rel="nofollow ugc">Privacy Policy</a>
What data is sent and when? 
When any plugin or WordPress core feature attempts to send an email (e.g. password resets, contact form submissions, order confirmations), the data (including the recipient’s email address, sender information, email subject, and email body content) is transmitted securely to your configured provider in order to deliver the email. No data is sent if you have not configured an API key for a provider.

Magic API Email

Send WordPress emails through a transactional API provider: Resend, Mailgun, Postmark, or Mailtrap. No SMTP needed.

tmertz

This plugin replaces wp_mail with a custom function that utilizes PostMarkApp.com to send email to your users. 
There really isn’t much more to say about the plugin.
<h4>REQUIRED</h4>
<ul>
<li>PHP5</li>
<li>cURL for PHP5</li>
</ul>

PostMarkApp Mail Replacement

A simple plugin that replaces the default wp_mail function with PostMarkApp (http://postmarkapp.com/).

Magic API Email vs PostMarkApp Mail Replacement