I see a lot of complaints that Outlook won't send email and returns error code 0x800CC80.
The error code 0x800CC80 comes up with the message "none of the authentication methods supported by this client are supported by your server."
This is caused by incorrect server settings, often due to an anti-virus scanner that installs an Outlook add-in. One easy test is to close Outlook and restart it in Safe mode. If mail sends in Safe mode, check your add-ins. Norton Internet Security, AVG, and others are known to install add-ins.
To open Outlook in Safe mode: Close Outlook then hold Ctrl as you click on the Outlook icon. You'll get a message asking if you want to start in Safe mode. Click Ok.
To let Outlook try to fix it, you can use the Repair option in Account Settings.
In Microsoft Outlook 2007, go to Tools > Account Settings > Email.
In Outlook 2010 or Outlook 2013, go to File > Account Settings > Email.
Select the problem account and press Repair.
If repair fails or if you want to check the settings yourself, double click the account in Account Settings then click More Settings.
On the Advanced tab, verify the SMTP port number and SSL setting is correct. Check with your email provider's support staff or web site to get the current server names.
On the Outgoing Server tab, check your authentication settings. Try changing the setting for Log on to incoming mail server before sending mail.
Anti-Virus Add-ins
If an add-in is the problem, you can disable the add-in. In Outlook 2010 or 2013, look for Add-ins in File, Options, Add-ins, or Tools, Trust Center, Add-ins menu in Outlook 2007.
Click the Go button at the bottom of the page and deselect the anti-virus add-in.
what if none of the above works?