Cannot connect to Email account
I added my email to apple email, and it always disconnects, it has a symbol like a thunder next to my email, if I click it, it says "can't connect to the account, enter the password for user account", I entered the email password, it didn't work, then I entered my computer password, it didn't work either, anyone can help me with this? I have been having this problem for a couple of years, couldn't resolve. Thank you!
[Re-Titled by Moderator]
MacBook Pro 13″, macOS 10.12