diff --git a/packages/backend/src/plugins/auth.ts b/packages/backend/src/plugins/auth.ts
index fb555cd..f6dbdd2 100644
--- a/packages/backend/src/plugins/auth.ts
+++ b/packages/backend/src/plugins/auth.ts
@@ -5,7 +5,7 @@ import {
 } from '@backstage/plugin-auth-backend';
 import { Router } from 'express';
 import { PluginEnvironment } from '../types';
-import { DEFAULT_NAMESPACE, stringifyEntityRef, } from '@backstage/catalog-model';
+import { resolverResult } from './plugins_helper/googleAuthResolver';
 
 export default async function createPlugin(
   env: PluginEnvironment,
@@ -52,32 +52,9 @@ export default async function createPlugin(
       }),
       google: providers.google.create({
         signIn: {
-          resolver: async ({ profile }, ctx) => {
-            if (!profile.email) {
-              throw new Error(
-                'Login failed, user profile does not contain an email',
-              );
-            }
-            const [localPart, domain] = profile.email.split('@');
-            if (domain !== 'code.berlin') {
-              throw new Error(
-                `Login failed, '${profile.email}' does not belong to the expected domain`,
-              );
-            }
-            const userEntityRef = stringifyEntityRef({
-              kind: 'User',
-              name: localPart,
-              namespace: DEFAULT_NAMESPACE,
-            });
-            return ctx.issueToken({
-              claims: {
-                sub: userEntityRef,
-                ent: [userEntityRef],
-              },
-            });
-          },
+          resolver: resolverResult,
         },
       }),
-      },
-});
+    },
+  });
 }
diff --git a/packages/backend/src/plugins/plugins_helper/googleAuthResolver.ts b/packages/backend/src/plugins/plugins_helper/googleAuthResolver.ts
new file mode 100644
index 0000000..b6633d3
--- /dev/null
+++ b/packages/backend/src/plugins/plugins_helper/googleAuthResolver.ts
@@ -0,0 +1,43 @@
+import {
+  stringifyEntityRef,
+  DEFAULT_NAMESPACE,
+} from '@backstage/catalog-model';
+import { OAuthResult } from '@backstage/plugin-auth-backend';
+import { SignInInfo, AuthResolverContext } from '@backstage/plugin-auth-node';
+
+export const resolverResult = async (
+  profile_input: SignInInfo<OAuthResult>,
+  ctx: AuthResolverContext,
+) => {
+  const profile = profile_input.profile;
+  const regexp = new RegExp(
+    /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/,
+  );
+
+  if (!profile.email || !regexp.test(profile.email)) {
+    throw new Error(
+      'Login failed, user profile does not contain a valid email',
+    );
+  }
+
+  const [localPart, domain] = profile.email.split('@');
+
+  if (domain !== 'code.berlin') {
+    throw new Error(
+      `Login failed, '${profile.email}' does not belong to the expected domain`,
+    );
+  }
+
+  const userEntityRef = stringifyEntityRef({
+    kind: 'User',
+    name: localPart,
+    namespace: DEFAULT_NAMESPACE,
+  });
+  
+  return ctx.issueToken({
+    claims: {
+      sub: userEntityRef,
+      ent: [userEntityRef],
+    },
+  });
+};