diff --git a/frontend/src/components/domains/DomainAliasForm.vue b/frontend/src/components/domains/DomainAliasForm.vue
index 791ab59bb..3807b016f 100644
--- a/frontend/src/components/domains/DomainAliasForm.vue
+++ b/frontend/src/components/domains/DomainAliasForm.vue
@@ -45,8 +45,6 @@
   <v-card-actions>
     <v-spacer></v-spacer>
     <v-btn
-      color="grey darken-1"
-      text
       @click="close"
       >
       <translate>Close</translate>
@@ -54,14 +52,12 @@
     <v-btn
       v-if="domainAlias && domainAlias.pk"
       color="error"
-      text
       @click="deleteAlias"
       >
       <translate>Delete</translate>
     </v-btn>
     <v-btn
-      color="primary darken-1"
-      text
+      color="primary"
       @click="submit"
       >
       {{ submitLabel }}
diff --git a/frontend/src/components/domains/DomainDNSConfig.vue b/frontend/src/components/domains/DomainDNSConfig.vue
index 363f932ee..c26b446d1 100644
--- a/frontend/src/components/domains/DomainDNSConfig.vue
+++ b/frontend/src/components/domains/DomainDNSConfig.vue
@@ -70,7 +70,7 @@ autodiscover.{{ domain.name }}. IN CNAME <strong>[<translate>hostname of your au
   </v-card-text>
   <v-card-actions>
     <v-spacer></v-spacer>
-    <v-btn color="grey darken-1" text @click="close">
+    <v-btn @click="close">
       <translate>Close</translate>
     </v-btn>
   </v-card-actions>
diff --git a/frontend/src/components/domains/DomainForm.vue b/frontend/src/components/domains/DomainForm.vue
index ad52fb1e1..3baffb81a 100644
--- a/frontend/src/components/domains/DomainForm.vue
+++ b/frontend/src/components/domains/DomainForm.vue
@@ -147,7 +147,7 @@
     </v-expansion-panel>
   </v-expansion-panels>
   <div class="mt-4 d-flex justify-end">
-    <v-btn color="grey lighten-1" @click="$router.go(-1)">
+    <v-btn @click="$router.go(-1)">
       <translate>Cancel</translate>
     </v-btn>
     <v-btn class="ml-4" color="primary darken-1" @click="save">
diff --git a/frontend/src/components/identities/AccountForm.vue b/frontend/src/components/identities/AccountForm.vue
index c56e7c477..3d071b8c3 100644
--- a/frontend/src/components/identities/AccountForm.vue
+++ b/frontend/src/components/identities/AccountForm.vue
@@ -114,7 +114,7 @@
     </v-expansion-panel>
   </v-expansion-panels>
   <div class="mt-4 d-flex justify-end">
-    <v-btn color="grey lighten-1" @click="$router.go(-1)">
+    <v-btn @click="$router.go(-1)">
       <translate>Cancel</translate>
     </v-btn>
     <v-btn class="ml-4" color="primary darken-1" @click="save">
diff --git a/frontend/src/components/identities/AliasForm.vue b/frontend/src/components/identities/AliasForm.vue
index 2a5fd5e96..38a279b1c 100644
--- a/frontend/src/components/identities/AliasForm.vue
+++ b/frontend/src/components/identities/AliasForm.vue
@@ -70,7 +70,7 @@
     </v-expansion-panel>
   </v-expansion-panels>
   <div class="mt-4 d-flex justify-end">
-    <v-btn color="grey lighten-1" @click="$router.go(-1)">
+    <v-btn @click="$router.go(-1)">
       <translate>Cancel</translate>
     </v-btn>
     <v-btn class="ml-4" color="primary darken-1" @click="save">
diff --git a/modoboa/admin/api/v2/serializers.py b/modoboa/admin/api/v2/serializers.py
index e520e71ff..8ffcf3807 100644
--- a/modoboa/admin/api/v2/serializers.py
+++ b/modoboa/admin/api/v2/serializers.py
@@ -404,7 +404,7 @@ class WritableAccountSerializer(v1_serializers.WritableAccountSerializer):
                     data["mailbox"] = {
                         "use_domain_quota": True
                     }
-        if "mailbox" in data:
+        if "mailbox" in data and "username" in data:
             self.address, domain_name = email_utils.split_mailbox(data["username"])
             self.domain = get_object_or_404(
                 models.Domain, name=domain_name)
@@ -421,7 +421,7 @@ class WritableAccountSerializer(v1_serializers.WritableAccountSerializer):
                         object_type="mailboxes")
                 except lib_exceptions.ModoboaException as inst:
                     raise serializers.ValidationError({
-                        "mailbox": force_text(inst)
+                        "mailbox": str(inst)
                     })
         if data.get("password") or not self.partial:
             password = data.get("password")