My email host supports both POP3 and IMAP retrieval, and for years, I've been using POP3 in Thunderbird to retrieve my email. I'd like to switch to IMAP so that messages can be easily stored on the server and automatically backed up by my email host.
If I switch Thunderbird from POP3 to IMAP mode for that account, what happens to the messages currently in my inbox and other folders in Thunderbird? Will TB try to upload them to the server, or delete them because they're not on the server, or something else odd? Or will they simply remain on the client without being on the server, and only new mail will be synchronized with the server?
Thanks for your help.