If the option Leave a copy of the message on the server is missing in Microsoft Outlook, it may be because of the type of email account you use. Of the most common types of email accounts, only POP3 accounts to download the email to your computer.
If you have an IMAP, or HTTP (such as Gmail or Outlook.com) account, the mail isn't stored on your computer. All email remains on the mail server until you delete it.
Steps to enable the option
To enable (or disable) the Leave a copy of the message on the server option, follow these steps:
1. Open Outlook.
2. Click the File tab > Account settings > Account settings.
3. Highlight your current POP3 account and click Change.
- Note: The window that opens will tell you what type of email account you have. (Look under Type.)
4. Choose More settings and click Advanced.
5. You should see a check box titled: Leave a copy of messages on the server.
6. Check the box to enable Leave a copy of the message on the server.
- Note: Enabling Leave a copy of the message on the server will allow you to access your email from multiple computers.