Hello

you mean like the first option that pops out of an internet search for 'thunderbird switch imap to pop' ?

https://support.mozilla.org/en-US/kb/faq-changing-imap-pop

this one ?

Please see attached. Instruction says to click on "leave messages on server." (last sentence on first attachment - server setting 2). However, I don't see that option. (see second attachment - server setting 1)

if you want to connect to an Imap server - and keep mails on server since it's the whole purpose of an Imap server is to keep mails on the server - setup the account as type 'imap'. If you want to use Pop3 and still keep mails on the server (possible but not the primary purpose of a Pop server and generally less manageable), setup your account as type 'pop3'.

I have already set it up as a PoP3 server. You say it is "possible" to set up to keep e-mails on server.

I have already set it up as a PoP3 server.

that's not what can be read on your screenshots. They are displaying 'Imap mail server'.

You might have enabled pop capablity on the mail server account.

But as gp states, you have not defined the account to Thunderbird as a pop account.

You might want to state why it is you think you need to use pop.