Q:

How to set Thunderbird leave messages on server in Ubuntu 18.04?

I'm trying to set up Thunderbird with secondary mail account and want it to leave messages on server. There was such a feature, at least in Windows earlier, like this: 

But I can't see those tick box in current setup of the newest Thunderbird in Ubuntu 18.04:

How to set the email client in proper way?
Update:
If you want to setup POP protocol in Thunderbird, you may do it manually this way if you need it.

A:

In the screenshots, note the different server types. IMAP always leaves messages on the server, while POP3 can be configured to leave messages on the server or not.
More details: Email: What’s the Difference Between POP3, IMAP, and Exchange? - How to Geek

