diff --git a/datahub-frontend/app/controllers/AuthenticationController.java b/datahub-frontend/app/controllers/AuthenticationController.java
index 4f89f4f67e149..47e893ca70d5e 100644
--- a/datahub-frontend/app/controllers/AuthenticationController.java
+++ b/datahub-frontend/app/controllers/AuthenticationController.java
@@ -27,6 +27,7 @@
 import org.pac4j.play.store.PlaySessionStore;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import play.data.validation.Constraints;
 import play.libs.Json;
 import play.mvc.Controller;
 import play.mvc.Http;
@@ -199,7 +200,8 @@ public Result signUp(Http.Request request) {
             return Results.badRequest(invalidCredsJson);
         }
 
-        if (StringUtils.isBlank(email)) {
+        Constraints.EmailValidator emailValidator = new Constraints.EmailValidator();
+        if (StringUtils.isBlank(email) || !emailValidator.isValid(email)) {
             JsonNode invalidCredsJson = Json.newObject().put("message", "Email must not be empty.");
             return Results.badRequest(invalidCredsJson);
         }
diff --git a/metadata-service/auth-impl/src/main/java/com/datahub/authentication/user/NativeUserService.java b/metadata-service/auth-impl/src/main/java/com/datahub/authentication/user/NativeUserService.java
index 7f0c16d28f121..2e253796fc967 100644
--- a/metadata-service/auth-impl/src/main/java/com/datahub/authentication/user/NativeUserService.java
+++ b/metadata-service/auth-impl/src/main/java/com/datahub/authentication/user/NativeUserService.java
@@ -45,7 +45,11 @@ public void createNativeUser(@Nonnull String userUrnString, @Nonnull String full
     Objects.requireNonNull(authentication, "authentication must not be null!");
 
     final Urn userUrn = Urn.createFromString(userUrnString);
-    if (_entityService.exists(userUrn) || userUrn.toString().equals(SYSTEM_ACTOR)) {
+    if (_entityService.exists(userUrn)
+        // Should never fail these due to Controller level check, but just in case more usages get put in
+        || userUrn.toString().equals(SYSTEM_ACTOR)
+        || userUrn.toString().equals(DATAHUB_ACTOR)
+        || userUrn.toString().equals(UNKNOWN_ACTOR)) {
       throw new RuntimeException("This user already exists! Cannot create a new user.");
     }
     updateCorpUserInfo(userUrn, fullName, email, title, authentication);
diff --git a/metadata-service/auth-impl/src/test/java/com/datahub/authentication/user/NativeUserServiceTest.java b/metadata-service/auth-impl/src/test/java/com/datahub/authentication/user/NativeUserServiceTest.java
index b0b10af82155a..cb1246a105645 100644
--- a/metadata-service/auth-impl/src/test/java/com/datahub/authentication/user/NativeUserServiceTest.java
+++ b/metadata-service/auth-impl/src/test/java/com/datahub/authentication/user/NativeUserServiceTest.java
@@ -74,6 +74,16 @@ public void testCreateNativeUserUserAlreadyExists() throws Exception {
     _nativeUserService.createNativeUser(USER_URN_STRING, FULL_NAME, EMAIL, TITLE, PASSWORD, SYSTEM_AUTHENTICATION);
   }
 
+  @Test(expectedExceptions = RuntimeException.class, expectedExceptionsMessageRegExp = "This user already exists! Cannot create a new user.")
+  public void testCreateNativeUserUserDatahub() throws Exception {
+    _nativeUserService.createNativeUser(DATAHUB_ACTOR, FULL_NAME, EMAIL, TITLE, PASSWORD, SYSTEM_AUTHENTICATION);
+  }
+
+  @Test(expectedExceptions = RuntimeException.class, expectedExceptionsMessageRegExp = "This user already exists! Cannot create a new user.")
+  public void testCreateNativeUserUserSystemUser() throws Exception {
+    _nativeUserService.createNativeUser(SYSTEM_ACTOR, FULL_NAME, EMAIL, TITLE, PASSWORD, SYSTEM_AUTHENTICATION);
+  }
+
   @Test
   public void testCreateNativeUserPasses() throws Exception {
     when(_entityService.exists(any())).thenReturn(false);
diff --git a/metadata-service/auth-servlet-impl/src/main/java/com/datahub/auth/authentication/AuthServiceController.java b/metadata-service/auth-servlet-impl/src/main/java/com/datahub/auth/authentication/AuthServiceController.java
index b5ce99902108a..34354a47b7f04 100644
--- a/metadata-service/auth-servlet-impl/src/main/java/com/datahub/auth/authentication/AuthServiceController.java
+++ b/metadata-service/auth-servlet-impl/src/main/java/com/datahub/auth/authentication/AuthServiceController.java
@@ -12,6 +12,7 @@
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.JsonNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.linkedin.common.urn.CorpuserUrn;
 import com.linkedin.common.urn.Urn;
 import com.linkedin.gms.factory.config.ConfigurationProvider;
 import java.util.concurrent.CompletableFuture;
@@ -28,6 +29,8 @@
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.client.HttpClientErrorException;
 
+import static com.linkedin.metadata.Constants.*;
+
 
 @Slf4j
 @RestController
@@ -177,6 +180,11 @@ CompletableFuture<ResponseEntity<String>> signUp(final HttpEntity<String> httpEn
     }
 
     String userUrnString = userUrn.asText();
+    String systemClientUser = new CorpuserUrn(_configProvider.getAuthentication().getSystemClientId()).toString();
+
+    if (userUrnString.equals(systemClientUser) || userUrnString.equals(DATAHUB_ACTOR) || userUrnString.equals(UNKNOWN_ACTOR)) {
+      return CompletableFuture.completedFuture(new ResponseEntity<>(HttpStatus.BAD_REQUEST));
+    }
     String fullNameString = fullName.asText();
     String emailString = email.asText();
     String titleString = title.asText();