diff --git a/notification-manager/src/main/java/de/itvsh/kop/notification/user/UserNotificationService.java b/notification-manager/src/main/java/de/itvsh/kop/notification/user/UserNotificationService.java
index 88d2070ce6870eeb18ac9dc8055dab8ffb417dcd..95cb74ff2e618b168d5b6aa76a454ba1c56cb6d3 100644
--- a/notification-manager/src/main/java/de/itvsh/kop/notification/user/UserNotificationService.java
+++ b/notification-manager/src/main/java/de/itvsh/kop/notification/user/UserNotificationService.java
@@ -1,10 +1,10 @@
 package de.itvsh.kop.notification.user;
 
 import java.util.List;
-
-import javax.validation.constraints.NotNull;
+import java.util.Objects;
 
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.scheduling.annotation.Async;
 import org.springframework.stereotype.Service;
 import org.springframework.validation.annotation.Validated;
 
@@ -24,8 +24,12 @@ public class UserNotificationService {
 	@Autowired
 	private UserRemoteService userRemoteService;
 
-	public void sendNotification(@NotNull String organisationEinheitId) {
-		var recipients = userRemoteService.getRecipients(organisationEinheitId);
+	@Async
+	public void sendNotification(String organisationsEinheitId) {
+		if (Objects.isNull(organisationsEinheitId)) {
+			throw new IllegalArgumentException("organisationsEinheitId cannot be null.");
+		}
+		var recipients = userRemoteService.getRecipients(organisationsEinheitId);
 		emailRemoteService.sendEmail(buildUserEmail(recipients));
 	}
 
diff --git a/notification-manager/src/test/java/de/itvsh/kop/notification/user/UserNotificationServiceTest.java b/notification-manager/src/test/java/de/itvsh/kop/notification/user/UserNotificationServiceTest.java
index 463469928c2c03bd1a5863679a861dbde33eda8f..37dd2dc0832eba1f26567a1db03a50cb3fe0eb5b 100644
--- a/notification-manager/src/test/java/de/itvsh/kop/notification/user/UserNotificationServiceTest.java
+++ b/notification-manager/src/test/java/de/itvsh/kop/notification/user/UserNotificationServiceTest.java
@@ -1,5 +1,6 @@
 package de.itvsh.kop.notification.user;
 
+import static org.assertj.core.api.Assertions.*;
 import static org.mockito.ArgumentMatchers.*;
 import static org.mockito.Mockito.*;
 
@@ -31,9 +32,9 @@ class UserNotificationServiceTest {
 	@Nested
 	class TestSendNotification {
 
-		@DisplayName("with valid orgaIds")
+		@DisplayName("with valid orgaId")
 		@Nested
-		class TestWithValidOrgaIds {
+		class TestWithValidOrgaId {
 
 			@BeforeEach
 			void init() {
@@ -55,5 +56,31 @@ class UserNotificationServiceTest {
 				verify(emailRemoteService).sendEmail(UserEmailTestFactory.create());
 			}
 		}
+
+		@DisplayName("with valid orgaId")
+		@Nested
+		class TestWithInValidOrgaId {
+
+			@Test
+			void shouldSendEmail() {
+				assertThatThrownBy(() -> service.sendNotification(null))
+						.isInstanceOf(IllegalArgumentException.class)
+						.withFailMessage("organisationsEinheitId cannot be null.");
+			}
+
+			@Test
+			void shouldNotCallUserRemoteService() {
+				assertThatThrownBy(() -> service.sendNotification(null));
+
+				verify(userRemoteService, never()).getRecipients(anyString());
+			}
+
+			@Test
+			void shouldNotCallEmailRemoteSErvie() {
+				assertThatThrownBy(() -> service.sendNotification(null));
+
+				verify(emailRemoteService, never()).sendEmail(any(UserEmail.class));
+			}
+		}
 	}
 }
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