Here’s the first thing to look at for a fix for this issue:
Your Office 365 connection may be failing on IPv6
Things are changing quickly with the adoption of IPv6 addressing. At nearly every step along the way between the seat you sit in and where you ultimately need to connect there’s a lot that may or may not be fully compatible with the IPv6 protocol.
e.g. Network adapters, routers, switches, ISPs, servers, etc.
It is possible that trying to connect over the IPv6 network is most likely the reason your Outlook (2007 – current) is having connection problems.
This could be because:
- You are using an out of date hardware/firmware
- You have network adapters that are really out of date.
- You have an unsupported operating system like Vista or XP
If there isn’t a glaring root cause of your IPv6 network problem you can try to work around the issue by trying to disable the IPv6 settings on the active network adapter you are using.
Here are the steps:
- Click “Start”, and then go to your Control Panel.
- Click “Network and Sharing Center”.
- Click on the Network Connection you are currently using. Look for any that should not be running and disable them (e.g. extra VPN connections or tunnels)
- Click “Properties” on the active network connection.
- Click on the “Networking” tab, then uncheck TCP/IPv6 check box. Then click “OK” to continue.
Now try to connect again using Outlook and see if the problem has resolved.