diff --git a/wp-includes/formatting.php b/wp-includes/formatting.php
index fbcde5630b..4c229b7796 100644
--- a/wp-includes/formatting.php
+++ b/wp-includes/formatting.php
@@ -4244,8 +4244,60 @@ function wp_staticize_emoji( $text ) {
  * @return array The email data array, with emoji in the message staticized.
  */
 function _wp_staticize_emoji_for_email( $mail ) {
-	if ( isset( $mail['message'] ) ) {
+	if ( ! isset( $mail['message'] ) ) {
+		return $mail;
+	}
+
+	/*
+	 * We can only transform the emoji into images if it's a text/html email.
+	 * To do that, here's a cut down version of the same process that happens
+	 * in wp_mail() - get the Content-Type from the headers, if there is one,
+	 * then pass it through the wp_mail_content_type filter, in case a plugin
+	 * is handling changing the Content-Type.
+	 */
+	$headers = array();
+	if ( isset( $mail['headers'] ) ) {
+		if ( is_array( $mail['headers'] ) ) {
+			$headers = $mail['headers'];
+		} else {
+			$headers = explode( "\n", str_replace( "\r\n", "\n", $mail['headers'] ) );
+		}
+	}
+
+	foreach ( $headers as $header ) {
+		if ( strpos($header, ':') === false ) {
+			continue;
+		}
+
+		// Explode them out
+		list( $name, $content ) = explode( ':', trim( $header ), 2 );
+
+		// Cleanup crew
+		$name    = trim( $name    );
+		$content = trim( $content );
+
+		if ( 'content-type' === strtolower( $name ) ) {
+			if ( strpos( $content, ';' ) !== false ) {
+				list( $type, $charset ) = explode( ';', $content );
+				$content_type = trim( $type );
+			} else {
+				$content_type = trim( $content );
+			}
+			break;
+		}
+	}
+
+	// Set Content-Type if we don't have a content-type from the input headers
+	if ( ! isset( $content_type ) ) {
+		$content_type = 'text/plain';
+	}
+
+	/** This filter is documented in wp-includes/pluggable.php */
+	$content_type = apply_filters( 'wp_mail_content_type', $content_type );
+
+	if ( 'text/html' === $content_type ) {
 		$mail['message'] = wp_staticize_emoji( $mail['message'], true );
 	}
+
 	return $mail;
 }