diff --git a/frontend/src/api/repository.js b/frontend/src/api/repository.js
index 459935c68..69c2bea6e 100644
--- a/frontend/src/api/repository.js
+++ b/frontend/src/api/repository.js
@@ -42,8 +42,9 @@ _axios.interceptors.response.use(
         !error.config.ignoreErrors
       ) {
         const busStore = useBusStore()
+        const msg = error.response.data?.error || error.response.data
         busStore.displayNotification({
-          msg: error.response.data,
+          msg,
           type: 'error',
         })
       }
diff --git a/frontend/src/components/account/ForwardForm.vue b/frontend/src/components/account/ForwardForm.vue
index 4610c0e8e..223377bf3 100644
--- a/frontend/src/components/account/ForwardForm.vue
+++ b/frontend/src/components/account/ForwardForm.vue
@@ -28,7 +28,7 @@
   </v-card>
 </template>
 
-<script setup lang="js">
+<script setup>
 import { ref } from 'vue'
 import { useGettext } from 'vue3-gettext'
 import accountApi from '@/api/account'
@@ -40,15 +40,17 @@ const busStore = useBusStore()
 const form = ref({})
 const loading = ref(false)
 
-function submit() {
+async function submit() {
   loading.value = true
-  accountApi.setForward(form.value).then(() => {
-    loading.value = false
+  try {
+    await accountApi.setForward(form.value)
     busStore.displayNotification({
       type: 'success',
       msg: $gettext('Forward updated'),
     })
-  })
+  } finally {
+    loading.value = false
+  }
 }
 
 accountApi.getForward().then((resp) => {
diff --git a/modoboa/admin/api/v2/serializers.py b/modoboa/admin/api/v2/serializers.py
index ef2a9b1fb..de29a9f21 100644
--- a/modoboa/admin/api/v2/serializers.py
+++ b/modoboa/admin/api/v2/serializers.py
@@ -246,12 +246,8 @@ class AdminGlobalParametersSerializer(serializers.Serializer):
 
     # Aliases settings
     alias_can_target_any_domain = serializers.BooleanField(default=True)
-    alias_target_block_list = serializers.ListField(
-        child=serializers.CharField(), required=False
-    )
-    alias_target_allow_list = serializers.ListField(
-        child=serializers.CharField(), required=False
-    )
+    alias_target_block_list = serializers.CharField(required=False, allow_null=True)
+    alias_target_allow_list = serializers.CharField(required=False, allow_null=True)
 
     def validate_default_domain_quota(self, value):
         """Ensure quota is a positive integer."""
diff --git a/modoboa/admin/models/alias.py b/modoboa/admin/models/alias.py
index 1ded3caf3..83f2413cc 100644
--- a/modoboa/admin/models/alias.py
+++ b/modoboa/admin/models/alias.py
@@ -91,16 +91,21 @@ class AliasManager(models.Manager):
         )
 
 
+def convert_to_list(raw_value: str) -> list[str]:
+    """Convert input string to list of string."""
+    return [item.strip() for item in raw_value.split(",")]
+
+
 def is_alias_target_allowed(domain: str) -> bool:
     """Check if alias target is allowed or not."""
     params = dict(param_tools.get_global_parameters(app="admin"))
     if params.get("alias_can_target_any_domain"):
-        blocked_domains = params.get("alias_target_block_list", "").split(",")
-        if domain in blocked_domains:
+        blocked_domains = params.get("alias_target_block_list")
+        if blocked_domains and domain in convert_to_list(blocked_domains):
             return False
     else:
-        allowed_domains = params.get("alias_target_allow_list", "").split(",")
-        if domain not in allowed_domains:
+        allowed_domains = params.get("alias_target_allow_list")
+        if allowed_domains and domain not in convert_to_list(allowed_domains):
             return False
     return True