diff --git a/grok_register_ttk.py b/grok_register_ttk.py
index 0a24f0c..8e6e677 100644
--- a/grok_register_ttk.py
+++ b/grok_register_ttk.py
@@ -37,7 +37,9 @@ DEFAULT_CONFIG = {
     "cloudflare_path_token": "/api/token",
     "cloudflare_path_messages": "/api/mails",
     # ===== 自建临时邮箱 mail.bblbb.com（任意 local-part 可收，Header X-Api-Key）=====
+    # 注意：若本地已有 config.json，其中的 email_provider / defaultDomains 会覆盖此处默认值。
     "email_provider": "bblbb",
+    "defaultDomains": "mail.bblbb.com",
     "bblbb_api_base": "https://mail.bblbb.com",
     "bblbb_api_key": "",
     "bblbb_domain": "mail.bblbb.com",
@@ -1103,7 +1105,7 @@ def pick_domain(api_key=None):
 
 
 def get_email_provider():
-    return str(config.get("email_provider", "duckmail") or "duckmail").strip().lower()
+    return str(config.get("email_provider", "bblbb") or "bblbb").strip().lower()
 
 
 def get_bblbb_api_base():