fix: resolve default sender to canonical identity on local-part login

When authenticating with a local-part username (e.g. 'user' instead of
'user@domain.tld') on Stalwart 0.15.x, the default sender could resolve
to an alias identity instead of the canonical mailbox address.

- Add emailMatchesUsername() helper that matches local-part usernames
  against full email addresses (e.g. 'user' matches 'user@domain.tld')
- Prefer canonical identities (mayDelete=false) over aliases as tiebreaker
- Add preferredPrimaryId to identity store (persisted to localStorage)
  so users can explicitly set their default sender
- Add 'Set as Primary' star button in identity manager modal
- Fix sendEmail() fallback identity resolution for local-part usernames
- Add i18n strings for all 8 supported locales

Fixes #43

components/identity/identity-manager-modal.tsx

@@ -2,7 +2,7 @@
 
 import { useEffect, useState, useCallback } from 'react';
 import { useTranslations } from 'next-intl';
-import { X, Mail, Pencil, Trash2, Plus, AlertTriangle } from 'lucide-react';
+import { X, Mail, Pencil, Trash2, Plus, AlertTriangle, Star } from 'lucide-react';
 import { cn } from '@/lib/utils';
 import { Button } from '@/components/ui/button';
 import { ConfirmDialog } from '@/components/ui/confirm-dialog';
@@ -19,6 +19,12 @@ import { toast } from '@/stores/toast-store';
 import { useFocusTrap } from '@/hooks/use-focus-trap';
 import { useConfirmDialog } from '@/hooks/use-confirm-dialog';
 
+function emailMatchesUsername(email: string, username: string): boolean {
+  if (email === username) return true;
+  if (!username.includes('@') && email.split('@')[0] === username) return true;
+  return false;
+}
+
 interface IdentityFormData {
   name: string;
   email: string;
@@ -39,6 +45,8 @@ export function IdentityManagerModal({ isOpen, onClose }: IdentityManagerModalPr
 
   const client = useAuthStore((state) => state.client);
   const identities = useIdentityStore((state) => state.identities);
+  const preferredPrimaryId = useIdentityStore((state) => state.preferredPrimaryId);
+  const setPreferredPrimary = useIdentityStore((state) => state.setPreferredPrimary);
   const syncIdentities = useSyncIdentities();
 
   const [editingId, setEditingId] = useState<string | null>(null);
@@ -52,11 +60,26 @@ export function IdentityManagerModal({ isOpen, onClose }: IdentityManagerModalPr
     try {
       const serverIdentities = await client.getIdentities();
       const username = useAuthStore.getState().username;
+      const preferredPrimaryId = useIdentityStore.getState().preferredPrimaryId;
       const sorted = [...serverIdentities].sort((a, b) => {
-        const aMatch = a.email === username ? -1 : 0;
-        const bMatch = b.email === username ? -1 : 0;
-        return aMatch - bMatch;
+        const aMatch = emailMatchesUsername(a.email, username || '');
+        const bMatch = emailMatchesUsername(b.email, username || '');
+        if (aMatch && !bMatch) return -1;
+        if (!aMatch && bMatch) return 1;
+        if (aMatch && bMatch) {
+          if (!a.mayDelete && b.mayDelete) return -1;
+          if (a.mayDelete && !b.mayDelete) return 1;
+        }
+        return 0;
       });
+      // Move preferred primary to front if set
+      if (preferredPrimaryId) {
+        const idx = sorted.findIndex((id) => id.id === preferredPrimaryId);
+        if (idx > 0) {
+          const [preferred] = sorted.splice(idx, 1);
+          sorted.unshift(preferred);
+        }
+      }
       useIdentityStore.getState().setIdentities(sorted);
       syncIdentities();
     } catch (error) {
@@ -168,6 +191,15 @@ export function IdentityManagerModal({ isOpen, onClose }: IdentityManagerModalPr
     }
   }, [client, refreshIdentities, t, tNotif, confirmDialog]);
 
+  const handleSetPrimary = useCallback((identity: Identity) => {
+    setPreferredPrimary(identity.id);
+    // Re-sort: move the preferred identity to the front
+    const reordered = [identity, ...identities.filter((id) => id.id !== identity.id)];
+    useIdentityStore.getState().setIdentities(reordered);
+    syncIdentities();
+    toast.success(tNotif('identity_set_primary'));
+  }, [identities, setPreferredPrimary, syncIdentities, tNotif]);
+
   if (!isOpen) return null;
 
   return (
@@ -281,6 +313,17 @@ export function IdentityManagerModal({ isOpen, onClose }: IdentityManagerModalPr
 
                       {/* Actions */}
                       <div className="flex items-center gap-2">
+                        {identities[0]?.id !== identity.id && identities.length > 1 && (
+                          <Button
+                            variant="ghost"
+                            size="sm"
+                            onClick={() => handleSetPrimary(identity)}
+                            disabled={!!editingId || isCreating}
+                            title={t('set_as_primary')}
+                          >
+                            <Star className="w-4 h-4" />
+                          </Button>
+                        )}
                         <Button
                           variant="ghost"
                           size="sm"

lib/jmap/client.ts

@@ -1425,7 +1425,9 @@ export class JMAPClient {
       if (identityResponse.methodResponses?.[0]?.[0] === "Identity/get") {
         const identities = (identityResponse.methodResponses[0][1].list || []) as { id: string; email: string }[];
         if (identities.length > 0) {
-          const matchingIdentity = identities.find((id) => id.email === (fromEmail || this.username));
+          const target = fromEmail || this.username;
+          const matchingIdentity = identities.find((id) => id.email === target)
+            || (!target.includes('@') ? identities.find((id) => id.email.split('@')[0] === target) : undefined);
           finalIdentityId = matchingIdentity?.id || identities[0].id;
         }
       }

locales/de/common.json

@@ -519,6 +519,7 @@
     "identity_created": "Identität erfolgreich erstellt",
     "identity_updated": "Identität erfolgreich aktualisiert",
     "identity_deleted": "Identität gelöscht",
+    "identity_set_primary": "Primäre Identität aktualisiert",
     "identity_create_failed": "Identität erstellen fehlgeschlagen: {error}",
     "identity_update_failed": "Identität aktualisieren fehlgeschlagen: {error}",
     "identity_delete_failed": "Identität löschen fehlgeschlagen: {error}",
@@ -1367,6 +1368,7 @@
     "delete_confirm": "Diese Identität löschen? Dies kann nicht rückgängig gemacht werden.",
     "cannot_delete": "Diese Identität kann nicht gelöscht werden",
     "primary_identity": "Primär",
+    "set_as_primary": "Als primär festlegen",
     "no_identities": "Keine Identitäten gefunden",
     "display": {
       "reply_to": "Antwort an:",

locales/en/common.json

@@ -519,6 +519,7 @@
     "identity_created": "Identity created successfully",
     "identity_updated": "Identity updated successfully",
     "identity_deleted": "Identity deleted",
+    "identity_set_primary": "Primary identity updated",
     "identity_create_failed": "Failed to create identity: {error}",
     "identity_update_failed": "Failed to update identity: {error}",
     "identity_delete_failed": "Failed to delete identity: {error}",
@@ -1367,6 +1368,7 @@
     "delete_confirm": "Delete this identity? This cannot be undone.",
     "cannot_delete": "This identity cannot be deleted",
     "primary_identity": "Primary",
+    "set_as_primary": "Set as primary",
     "no_identities": "No identities found",
     "display": {
       "reply_to": "Reply-To:",

locales/es/common.json

@@ -519,6 +519,7 @@
     "identity_created": "Identidad creada exitosamente",
     "identity_updated": "Identidad actualizada exitosamente",
     "identity_deleted": "Identidad eliminada",
+    "identity_set_primary": "Identidad principal actualizada",
     "identity_create_failed": "Error al crear identidad: {error}",
     "identity_update_failed": "Error al actualizar identidad: {error}",
     "identity_delete_failed": "Error al eliminar identidad: {error}",
@@ -1367,6 +1368,7 @@
     "delete_confirm": "¿Eliminar esta identidad? Esto no se puede deshacer.",
     "cannot_delete": "Esta identidad no se puede eliminar",
     "primary_identity": "Principal",
+    "set_as_primary": "Establecer como principal",
     "no_identities": "No se encontraron identidades",
     "display": {
       "reply_to": "Responder a:",

locales/fr/common.json

@@ -519,6 +519,7 @@
     "identity_created": "Identité créée avec succès",
     "identity_updated": "Identité mise à jour avec succès",
     "identity_deleted": "Identité supprimée",
+    "identity_set_primary": "Identité principale mise à jour",
     "identity_create_failed": "Échec de la création de l'identité: {error}",
     "identity_update_failed": "Échec de la mise à jour de l'identité: {error}",
     "identity_delete_failed": "Échec de la suppression de l'identité: {error}",
@@ -1367,6 +1368,7 @@
     "delete_confirm": "Supprimer cette identité ? Cette action est irréversible.",
     "cannot_delete": "Cette identité ne peut pas être supprimée",
     "primary_identity": "Principale",
+    "set_as_primary": "Définir comme principale",
     "no_identities": "Aucune identité trouvée",
     "display": {
       "reply_to": "Répondre à :",

locales/it/common.json

@@ -519,6 +519,7 @@
     "identity_created": "Identità creata con successo",
     "identity_updated": "Identità aggiornata con successo",
     "identity_deleted": "Identità eliminata",
+    "identity_set_primary": "Identità principale aggiornata",
     "identity_create_failed": "Impossibile creare l'identità: {error}",
     "identity_update_failed": "Impossibile aggiornare l'identità: {error}",
     "identity_delete_failed": "Impossibile eliminare l'identità: {error}",
@@ -1367,6 +1368,7 @@
     "delete_confirm": "Eliminare questa identità? Questa azione non può essere annullata.",
     "cannot_delete": "Questa identità non può essere eliminata",
     "primary_identity": "Principale",
+    "set_as_primary": "Imposta come principale",
     "no_identities": "Nessuna identità trovata",
     "display": {
       "reply_to": "Rispondi a:",

locales/ja/common.json

@@ -519,6 +519,7 @@
     "identity_created": "送信者情報を作成しました",
     "identity_updated": "送信者情報を更新しました",
     "identity_deleted": "送信者情報を削除しました",
+    "identity_set_primary": "プライマリ送信者情報を更新しました",
     "identity_create_failed": "送信者情報の作成に失敗しました: {error}",
     "identity_update_failed": "送信者情報の更新に失敗しました: {error}",
     "identity_delete_failed": "送信者情報の削除に失敗しました: {error}",
@@ -1367,6 +1368,7 @@
     "delete_confirm": "この送信者情報を削除しますか？この操作は元に戻せません。",
     "cannot_delete": "この送信者情報は削除できません",
     "primary_identity": "プライマリ",
+    "set_as_primary": "プライマリに設定",
     "no_identities": "送信者情報が見つかりません",
     "display": {
       "reply_to": "返信先:",

locales/nl/common.json

@@ -519,6 +519,7 @@
     "identity_created": "Identiteit succesvol aangemaakt",
     "identity_updated": "Identiteit succesvol bijgewerkt",
     "identity_deleted": "Identiteit verwijderd",
+    "identity_set_primary": "Primaire identiteit bijgewerkt",
     "identity_create_failed": "Kan identiteit niet aanmaken: {error}",
     "identity_update_failed": "Kan identiteit niet bijwerken: {error}",
     "identity_delete_failed": "Kan identiteit niet verwijderen: {error}",
@@ -1367,6 +1368,7 @@
     "delete_confirm": "Deze identiteit verwijderen? Dit kan niet ongedaan worden gemaakt.",
     "cannot_delete": "Deze identiteit kan niet worden verwijderd",
     "primary_identity": "Primair",
+    "set_as_primary": "Instellen als primair",
     "no_identities": "Geen identiteiten gevonden",
     "display": {
       "reply_to": "Antwoord naar:",

locales/pt/common.json

@@ -519,6 +519,7 @@
     "identity_created": "Identidade criada com sucesso",
     "identity_updated": "Identidade atualizada com sucesso",
     "identity_deleted": "Identidade excluída",
+    "identity_set_primary": "Identidade principal atualizada",
     "identity_create_failed": "Falha ao criar identidade: {error}",
     "identity_update_failed": "Falha ao atualizar identidade: {error}",
     "identity_delete_failed": "Falha ao excluir identidade: {error}",
@@ -1367,6 +1368,7 @@
     "delete_confirm": "Excluir esta identidade? Isso não pode ser desfeito.",
     "cannot_delete": "Esta identidade não pode ser excluída",
     "primary_identity": "Principal",
+    "set_as_primary": "Definir como principal",
     "no_identities": "Nenhuma identidade encontrada",
     "display": {
       "reply_to": "Responder para:",

stores/auth-store.ts

@@ -52,12 +52,41 @@ function classifyLoginError(error: unknown): string {
   return 'generic';
 }
 
-function loadIdentities(rawIdentities: Identity[], username: string): { identities: Identity[]; primaryIdentity: Identity | null } {
-  const identities = [...rawIdentities].sort((a, b) => {
-    const aMatch = a.email === username ? -1 : 0;
-    const bMatch = b.email === username ? -1 : 0;
-    return aMatch - bMatch;
+function emailMatchesUsername(email: string, username: string): boolean {
+  if (email === username) return true;
+  // Handle local-part login: username "user" should match "user@domain.tld"
+  if (!username.includes('@') && email.split('@')[0] === username) return true;
+  return false;
+}
+
+function sortIdentities(rawIdentities: Identity[], username: string): Identity[] {
+  return [...rawIdentities].sort((a, b) => {
+    const aMatch = emailMatchesUsername(a.email, username);
+    const bMatch = emailMatchesUsername(b.email, username);
+    if (aMatch && !bMatch) return -1;
+    if (!aMatch && bMatch) return 1;
+    // Among matching identities, prefer canonical (non-deletable) over aliases
+    if (aMatch && bMatch) {
+      if (!a.mayDelete && b.mayDelete) return -1;
+      if (a.mayDelete && !b.mayDelete) return 1;
+    }
+    return 0;
   });
+}
+
+function loadIdentities(rawIdentities: Identity[], username: string): { identities: Identity[]; primaryIdentity: Identity | null } {
+  const preferredPrimaryId = useIdentityStore.getState().preferredPrimaryId;
+  const identities = sortIdentities(rawIdentities, username);
+
+  // If user has a preferred primary, move it to front
+  if (preferredPrimaryId) {
+    const idx = identities.findIndex((id) => id.id === preferredPrimaryId);
+    if (idx > 0) {
+      const [preferred] = identities.splice(idx, 1);
+      identities.unshift(preferred);
+    }
+  }
+
   const primaryIdentity = identities[0] ?? null;
   useIdentityStore.getState().setIdentities(identities);
   return { identities, primaryIdentity };

stores/identity-store.ts

@@ -15,6 +15,7 @@ interface IdentityStore {
   // Identity state (from server)
   identities: Identity[];
   selectedIdentityId: string | null;
+  preferredPrimaryId: string | null;
   isLoading: boolean;
   error: string | null;
 
@@ -27,6 +28,7 @@ interface IdentityStore {
   updateIdentityLocal: (identityId: string, updates: Partial<Identity>) => void;
   removeIdentity: (identityId: string) => void;
   selectIdentity: (identityId: string | null) => void;
+  setPreferredPrimary: (identityId: string | null) => void;
   setLoading: (loading: boolean) => void;
   setError: (error: string | null) => void;
   clearIdentities: () => void;
@@ -43,6 +45,7 @@ export const useIdentityStore = create<IdentityStore>()(
     (set, get) => ({
       identities: [],
       selectedIdentityId: null,
+      preferredPrimaryId: null,
       isLoading: false,
       error: null,
       subAddress: {
@@ -71,6 +74,8 @@ export const useIdentityStore = create<IdentityStore>()(
 
       selectIdentity: (identityId) => set({ selectedIdentityId: identityId }),
 
+      setPreferredPrimary: (identityId) => set({ preferredPrimaryId: identityId }),
+
       setLoading: (loading) => set({ isLoading: loading }),
 
       setError: (error) => set({ error }),
@@ -120,7 +125,8 @@ export const useIdentityStore = create<IdentityStore>()(
       name: 'identity-storage',
       // Only persist sub-addressing data, not identities (they're server-side)
       partialize: (state) => ({
-        subAddress: state.subAddress
+        subAddress: state.subAddress,
+        preferredPrimaryId: state.preferredPrimaryId,
       }),
     }
   )