diff --git a/goofy-server/src/main/java/de/itvsh/goofy/postfach/PostfachMailModelAssembler.java b/goofy-server/src/main/java/de/itvsh/goofy/postfach/PostfachMailModelAssembler.java
index 74734a95188d2896e2a6bd3f4dcc013f77f17278..0b49bcbc606db14e5096b9dea6af58360053a0b6 100644
--- a/goofy-server/src/main/java/de/itvsh/goofy/postfach/PostfachMailModelAssembler.java
+++ b/goofy-server/src/main/java/de/itvsh/goofy/postfach/PostfachMailModelAssembler.java
@@ -31,8 +31,8 @@ class PostfachMailModelAssembler implements RepresentationModelAssembler<Postfac
 	private static final Predicate<PostfachMail> HAS_ATTACHMENTS = nachricht -> !nachricht.getAttachments().isEmpty();
 
 	static final String SYSTEM_USER_IDENTIFIER = "system";
-	private static final Predicate<PostfachMail> SENT_BY_CLIENT_USER = postfachNachricht -> !postfachNachricht.getCreatedBy().toString()
-			.startsWith(SYSTEM_USER_IDENTIFIER);
+	private static final Predicate<PostfachMail> SENT_BY_CLIENT_USER = postfachNachricht -> Optional.ofNullable(postfachNachricht.getCreatedBy())
+			.map(createdBy -> !createdBy.toString().startsWith(SYSTEM_USER_IDENTIFIER)).orElse(false);
 
 	public CollectionModel<EntityModel<PostfachMail>> toCollectionModel(Stream<PostfachMail> entities, String vorgangId, long vorgangVersion,
 			Optional<String> postfachId) {
diff --git a/goofy-server/src/test/java/de/itvsh/goofy/postfach/PostfachMailModelAssemblerTest.java b/goofy-server/src/test/java/de/itvsh/goofy/postfach/PostfachMailModelAssemblerTest.java
index 8faa7b4cf65a9aebc068bcd67922978c6a53056e..100b7a73b6827e90dfd9af06f9aca36d7102f202 100644
--- a/goofy-server/src/test/java/de/itvsh/goofy/postfach/PostfachMailModelAssemblerTest.java
+++ b/goofy-server/src/test/java/de/itvsh/goofy/postfach/PostfachMailModelAssemblerTest.java
@@ -102,8 +102,15 @@ class PostfachMailModelAssemblerTest {
 
 				assertThat(link).isNotPresent();
 			}
-		}
 
+			@Test
+			void shouldNotBePresentOnNull() {
+				var link = modelAssembler.toModel(PostfachMailTestFactory.createBuilder().createdBy(null).build())
+						.getLink(PostfachMailModelAssembler.REL_CREATED_BY);
+
+				assertThat(link).isNotPresent();
+			}
+		}
 	}
 
 	@Nested