https://support.microsoft.com/en-us/kb/3134780

Outlook displays a "Disconnected" status when IPv6 is enabled

Method 1: Disable IPv6 on your network adapter

1. Click Start, and then click Control Panel.
2. Click Network and Sharing Center.
3. In the View your active networks area, click Local Area Connection, and then click Properties.
4. On the Networking tab, clear the Internet Protocol Version 6 (TCP/IPv6) check box, and then click OK.

Method 2: Download the fix that's associated with the "Prefer IPv4 over IPv6 in prefix policies" topic in the following Microsoft Knowledge Base article: