Downloading e-mails in the way first downloading the headers and then the body resulted often in deleting on the server, while the setting is "preserve on server". See also the discussion "how to selective download e-mails". Now I wanted to see how it goes about deletion if I should use the method of downloading whole e-mails (again with preserve-on-server-setting). And I observed also that often the e-mails on the server disappeared. What is / can be the cause? I use Thunderbird-version 45.8.0, with POP-communication.