diff --git a/src/wp-includes/ms-functions.php b/src/wp-includes/ms-functions.php
index 76b3ff5dc8..c81210042b 100644
--- a/src/wp-includes/ms-functions.php
+++ b/src/wp-includes/ms-functions.php
@@ -442,8 +442,11 @@ function wpmu_validate_user_signup($user_name, $user_email) {
 		$errors->add( 'user_name',  __( 'Sorry, that username is not allowed.' ) );
 	}
 
-	if ( is_email_address_unsafe( $user_email ) )
-		$errors->add('user_email',  __('You cannot use that email address to signup. We are having problems with them blocking some of our email. Please use another email provider.'));
+	if ( ! is_email( $user_email ) ) {
+		$errors->add( 'user_email', __( 'Please enter a valid email address.' ) );
+	} elseif ( is_email_address_unsafe( $user_email ) ) {
+		$errors->add( 'user_email', __( 'You cannot use that email address to signup. We are having problems with them blocking some of our email. Please use another email provider.' ) );
+	}
 
 	if ( strlen( $user_name ) < 4 )
 		$errors->add('user_name',  __( 'Username must be at least 4 characters.' ) );
@@ -456,9 +459,6 @@ function wpmu_validate_user_signup($user_name, $user_email) {
 	if ( preg_match( '/^[0-9]*$/', $user_name ) )
 		$errors->add('user_name', __('Sorry, usernames must have letters too!'));
 
-	if ( !is_email( $user_email ) )
-		$errors->add('user_email', __( 'Please enter a valid email address.' ) );
-
 	$limited_email_domains = get_site_option( 'limited_email_domains' );
 	if ( is_array( $limited_email_domains ) && ! empty( $limited_email_domains ) ) {
 		$emaildomain = substr( $user_email, 1 + strpos( $user_email, '@' ) );
diff --git a/tests/phpunit/tests/multisite/wpmuValidateUserSignup.php b/tests/phpunit/tests/multisite/wpmuValidateUserSignup.php
index 15cf56ca44..f5b3719fa4 100644
--- a/tests/phpunit/tests/multisite/wpmuValidateUserSignup.php
+++ b/tests/phpunit/tests/multisite/wpmuValidateUserSignup.php
@@ -122,6 +122,41 @@ class Tests_Multisite_WpmuValidateUserSignup extends WP_UnitTestCase {
 		$this->assertNotContains( 'user_email', $v['errors']->get_error_codes() );
 	}
 
+	public function test_invalid_email_address_with_no_banned_domains_results_in_error() {
+		$valid = wpmu_validate_user_signup( 'validusername', 'invalid-email' );
+
+		$this->assertContains( 'user_email', $valid['errors']->get_error_codes() );
+	}
+
+	public function test_invalid_email_address_with_banned_domains_results_in_error() {
+		update_site_option( 'banned_email_domains', "bar.com" );
+		$valid = wpmu_validate_user_signup( 'validusername', 'invalid-email' );
+		delete_site_option( 'banned_email_domains' );
+
+		$this->assertContains( 'user_email', $valid['errors']->get_error_codes() );
+	}
+
+	public function test_incomplete_email_address_with_no_banned_domains_results_in_error() {
+		$valid = wpmu_validate_user_signup( 'validusername', 'incomplete@email' );
+
+		$this->assertContains( 'user_email', $valid['errors']->get_error_codes() );
+	}
+
+	public function test_valid_email_address_matching_banned_domain_results_in_error() {
+		update_site_option( 'banned_email_domains', "bar.com" );
+		$valid = wpmu_validate_user_signup( 'validusername', 'email@bar.com' );
+		delete_site_option( 'banned_email_domains' );
+
+		$this->assertContains( 'user_email', $valid['errors']->get_error_codes() );
+	}
+
+	public function test_valid_email_address_not_matching_banned_domain_returns_in_success() {
+		update_site_option( 'banned_email_domains', "bar.com" );
+		$valid = wpmu_validate_user_signup( 'validusername', 'email@example.com' );
+		delete_site_option( 'banned_email_domains' );
+
+		$this->assertNotContains( 'user_email', $valid['errors']->get_error_codes() );
+	}
 }
 
 endif;