Người ta đã hướng dẫn cụ thể rùi mà sao không thực hiện! làm trên PC chứ ko phải ở BB:

" To leave email messages on your email server you may need to complete the following steps:

1. In your email client (Outlook, Thunderbird, etc.) on your computer, under Tools or Mail > Preferences.

2. Select your email account.

3. Locate advanced, server settings or options.

4. Select the option to leave email messages on the server.
Refer to your email client help for more information."