fix: subscribe newly created mailboxes #951

lib/__tests__/jmap-mailbox-account.test.ts

@@ -56,7 +56,7 @@ describe('JMAP mailbox mutations use the requested account', () => {
     expect(captured[0][0]).toBe('Mailbox/set');
     expect(captured[0][1].accountId).toBe('shared-account');
     expect(Object.values(captured[0][1].create as Record<string, unknown>))
-      .toEqual([{ name: 'Child', parentId: 'parent-id' }]);
+      .toEqual([{ name: 'Child', parentId: 'parent-id', isSubscribed: true }]);
     expect(mailbox).toMatchObject({
       id: 'created-mailbox',
       accountId: 'shared-account',

lib/jmap/client.ts

@@ -2691,7 +2691,10 @@ export class JMAPClient implements IJMAPClient {
   async createMailbox(name: string, parentId?: string, accountId?: string): Promise<Mailbox> {
     const targetAccountId = accountId || this.accountId;
     const createId = `new-${Date.now()}`;
-    const createData: Record<string, unknown> = { name };
+    // Subscribe explicitly: IMAP clients that list folders via LSUB
+    // (Thunderbird) hide unsubscribed mailboxes, and the server default is
+    // not guaranteed to be true. (#951)
+    const createData: Record<string, unknown> = { name, isSubscribed: true };
     if (parentId) {
       createData.parentId = parentId;
     }