diff --git a/src/wp-includes/pluggable.php b/src/wp-includes/pluggable.php
index 5d65e53f8b..c2a975d896 100644
--- a/src/wp-includes/pluggable.php
+++ b/src/wp-includes/pluggable.php
@@ -353,6 +353,8 @@ if ( ! function_exists( 'wp_mail' ) ) :
 		$phpmailer->clearAttachments();
 		$phpmailer->clearCustomHeaders();
 		$phpmailer->clearReplyTos();
+		$phpmailer->Body    = '';
+		$phpmailer->AltBody = '';
 
 		// Set "From" name and email.
 
diff --git a/tests/phpunit/tests/mail.php b/tests/phpunit/tests/mail.php
index c130658e3f..53eacbd7f5 100644
--- a/tests/phpunit/tests/mail.php
+++ b/tests/phpunit/tests/mail.php
@@ -475,4 +475,21 @@ class Tests_Mail extends WP_UnitTestCase {
 		$this->assertTrue( $result1 );
 		$this->assertFalse( $result2 );
 	}
+
+	/**
+	 * Tests that AltBody is reset between each wp_mail call.
+	 *
+	 * @covers :wp_mail
+	 */
+	public function test_wp_mail_resets_properties() {
+		$wp_mail_set_text_message = function ( $phpmailer ) {
+			$phpmailer->AltBody = 'user1';
+		};
+		add_action( 'phpmailer_init', $wp_mail_set_text_message );
+		wp_mail( 'user1@example.localhost', 'Test 1', '<p>demo</p>', 'Content-Type: text/html' );
+		remove_action( 'phpmailer_init', $wp_mail_set_text_message );
+		wp_mail( 'user2@example.localhost', 'Test 2', 'test2' );
+		$phpmailer = $GLOBALS['phpmailer'];
+		$this->assertNotSame( 'user1', $phpmailer->AltBody );
+	}
 }