Thanks for the reply everyone. Basically, I like gmail.com except gmail doesn't have sorting by sender and then by date for that sender. With Thunderbird, I forgot how I had it setted up but it has to be imap except this is the error I am getting and I don't know how to get around it. I know in the past, I can delete a message in Thunderbird but on gmail.com in the browser, it's still in the inbox and not moved to the trashcan like how it works when one deletes a message on gmail.com, it would go into the trash can.
Google basically blocks it from using and logging in to imap.gmail.com:
Sign-in attempt prevented
Someone just tried to sign in to your Google Account *****@gmail.com from an app that doesn't meet modern security standards.
Friday, January 8, 2016 10:57 PM (Pacific Standard Time)
We strongly recommend that you use a secure app, like Gmail, to access your account. All apps made by Google meet these security standards. Using a less secure app, on the other hand, could leave your account vulnerable. Learn more.