What are Less Secure Apps?
Less Secure Apps (LSA) are apps that don’t use OAuth (Open Authentication) to a code instead of a username and password to the mail server.
OAuth works by setting up a key and lock with Google and your email app the first time you use it, then it doesn’t need to send your username and password every time, meaning the connection is secure regardless of where you are.
Microsoft Outlook tries to use Basic Authentication, which doesn’t work with Google’s OAuth system and so you get an error 0x800CCC0E when you attempt to Send/Receive.
The solution used to be to turn on use Less Secure Apps but Google is phasing this out.
The solution is called 2-Step Verification, where you authenticate with something you know (your account name and password) with something you have (your phone) and then you can create a specific App Password that will only work with, in this case Microsoft Outlook.