Add option to force the from email

Author: MultiSuperFreek

page-settings.php

@@ -53,6 +53,10 @@
 	<?php if ( isset( $this->overridden_settings['sender_address'] ) ) : ?>
 		<div class="notice notice-info"><code>POSTMARK_SENDER_ADDRESS</code> is defined in your wp-config.php and overrides the <code>Sender Email</code> set here.</div>
 	<?php endif; ?>
+    
+    <?php if ( isset( $this->overridden_settings['sender_address'] ) ) : ?>
+        <div class="notice notice-info"><code>POSTMARK_FORCE_FROM</code> is defined in your wp-config.php and overrides the <code>Force From</code> set here.</div>
+    <?php endif; ?>
 
 	<div class="tab-content tab-general">
 		<table class="form-table">
@@ -84,6 +88,13 @@
 					<div class="footnote">This email must be a verified <a href="https://account.postmarkapp.com/signatures" target="_blank">Sender Signature</a>. It will appear as the "from" address on all outbound emails.</div>
 				</td>
 			</tr>
+            <tr>
+                <th><label>Force Sender Email</label></th>
+                <td>
+                    <input type="checkbox" class="pm-force-from" value="1" />
+                    <span class="footnote">Force emails to be sent from the Sender Email specified above. Disallows overriding using the <code>$headers</code> array.</span>
+                </td>
+            </tr>
 			<tr>
 				<th><label>Force HTML</label></th>
 				<td>
@@ -145,7 +156,7 @@
 		<pre>
 		$headers = array();
 
-		// Override the default 'From' address
+		// Override the default 'From' address if 'Force Sender Email' is not enabled
 		$headers['From'] = '[email protected]';
 
 		// Send the message as HTML

postmark-settings.php

@@ -10,6 +10,7 @@
     'api_key'        => defined( 'POSTMARK_API_KEY' ) ? POSTMARK_API_KEY : null,
     'stream_name'    => defined( 'POSTMARK_STREAM_NAME' ) ? POSTMARK_STREAM_NAME : null,
     'sender_address' => defined( 'POSTMARK_SENDER_ADDRESS' ) ? POSTMARK_SENDER_ADDRESS : null,
+    'force_from'     => defined( 'POSTMARK_FORCE_FROM' ) ? POSTMARK_FORCE_FROM : null,
 );
 $settings_from_constants = array_filter( $settings_from_constants );
 $settings = array_merge( $settings, $settings_from_constants );

postmark.php

@@ -81,6 +81,7 @@ public function load_settings() {
 				'api_key'        => get_option( 'postmark_api_key', '' ),
 				'stream_name'    => get_option( 'postmark_stream_name', 'outbound'),
 				'sender_address' => get_option( 'postmark_sender_address', '' ),
+                'force_from'     => get_option( 'postmark_force_from', 0 ),
 				'force_html'     => get_option( 'postmark_force_html', 0 ),
 				'track_opens'    => get_option( 'postmark_trackopens', 0 ),
 				'track_links'    => get_option( 'postmark_tracklinks', 0 ),
@@ -103,6 +104,12 @@ public function load_settings() {
 			update_option( 'postmark_settings', wp_json_encode( $settings ) );
 			return $settings;
 		}
+        
+        if ( is_array( $settings ) && ! isset( $settings['force_from'] ) ) {
+            $settings['force_from'] = 0;
+            update_option( 'postmark_settings', wp_json_encode( $settings ) );
+            return $settings;
+        }
 
 		return json_decode( $settings, true );
 	}
@@ -275,6 +282,13 @@ public function save_settings() {
 		} else {
 			$settings['sender_address'] = '';
 		}
+        
+        // We validate that 'force_from' is a numeric boolean.
+        if ( isset( $data['force_from'] ) && 1 === $data['force_from'] ) {
+            $settings['force_from'] = 1;
+        } else {
+            $settings['force_from'] = 0;
+        }
 
 		// We validate that 'force_html' is a numeric boolean.
 		if ( isset( $data['force_html'] ) && 1 === $data['force_html'] ) {

wp-mail.php

@@ -153,7 +153,7 @@ function wp_mail( $to, $subject, $message, $headers = '', $attachments = array()
 	// Allow overriding the From address when specified in the headers.
 	$from = $settings['sender_address'];
 
-	if ( isset( $recognized_headers['From'] ) ) {
+	if ( false === $settings['force_from'] && isset( $recognized_headers['From'] ) ) {
 		$from = $recognized_headers['From'];
 	}