I have recently discovered this error when I was not able to send and open a few of the emails. After facing this error Error 0x800ccc1a, I did some research on google regarding this error. Then, I got to know that it is an Outlook Sending error that occurs when there is an issue with SSL (Secure Socket Layer). After few minutes I found this amazing article that helped me to fix this Outlook sending error 0x800ccc1a. This write explains the main reasons behind this error and also discusses the 3 ways to fix this error 0x800ccc1a. These three methods are:

By Reconfiguring SSL Encryption.
By Changing The Port Numbers.
By Running Windows System File Checker.

Additionally, this blog also provides a professional software solution known as Outlook Email Recovery. It helps in managing and resolving all the Outlook PST file issues. If you are one of those who are facing this problem then you should check this write-up.