diff --git a/includes/class-wp-job-manager-email-notifications.php b/includes/class-wp-job-manager-email-notifications.php
index c6b6d7ed0..6455c3976 100644
--- a/includes/class-wp-job-manager-email-notifications.php
+++ b/includes/class-wp-job-manager-email-notifications.php
@@ -18,7 +18,7 @@ final class WP_Job_Manager_Email_Notifications {
 	const EMAIL_SETTING_PREFIX     = 'job_manager_email_';
 	const EMAIL_SETTING_ENABLED    = 'enabled';
 	const EMAIL_SETTING_PLAIN_TEXT = 'plain_text';
-	const MULTIPART_BOUNDARY       = '--jm-boundary';
+	const MULTIPART_BOUNDARY       = 'jm-boundary';
 
 	/**
 	 * Notifications to be scheduled.
@@ -976,6 +976,15 @@ private static function get_styles() {
 	private static function get_multipart_body( string $content_html, string $content_plain ): string {
 		$multipart_body = '';
 
+		if ( ! empty( $content_plain ) ) {
+
+			$multipart_body .= '
+--' . self::MULTIPART_BOUNDARY . '
+Content-Type: text/plain; charset="utf-8"
+
+' . $content_plain;
+		}
+
 		if ( ! empty( $content_html ) ) {
 			$multipart_body .= '
 --' . self::MULTIPART_BOUNDARY . '
@@ -984,13 +993,10 @@ private static function get_multipart_body( string $content_html, string $conten
 ' . $content_html;
 		}
 
-		if ( ! empty( $content_plain ) ) {
-
+		if ( ! empty( $multipart_body ) ) {
 			$multipart_body .= '
---' . self::MULTIPART_BOUNDARY . '
-Content-Type: text/plain; charset="utf-8"
-
-' . $content_plain;
+--' . self::MULTIPART_BOUNDARY . '--
+';
 		}
 
 		return $multipart_body;