Recently, we’ve had quite a few customers write in to complain that their copy of Outlook 2016 is behaving incorrectly: it is either deleting messages from the server when it is not supposed to do so, or it is downloading duplicate copies of mail from the server. This happens for POP accounts, not for IMAP accounts (which is what we normally recommend customers to use).
These problems happen because of a bug in Outlook 2016. Microsoft has a Web page that explains the problem as well as the solution (upgrade Outlook).
We’ve had reports of an error message like this in Outlook when using Windows 10:
error (0x800CCC13): Cannot connect to the network. Verify your network connection or modem.
If this happens to you, it’s because of a problem with Windows 10, not with Outlook or our servers. According to the Microsoft page about it, updating Windows 10 should fix it. If it doesn’t, they suggest using a “workaround” to repair corrupted files on your computer.
If you use Microsoft Outlook 2007 to read mail and you installed the December 2010 Outlook update, you might find that Outlook is slow to respond when you click between folders. Sometimes it can take several seconds.
This is caused by a bug in the Outlook update, not by a problem on our servers. To fix this, Microsoft recommends uninstalling the update for now.