Why does alpine seemingly remove messages on exit

I have a rather strange situation. I'm running a dovecot/postfix based mail server on debian. Most of the time everyone accesses the server using IMAP from their thunderbird/outlook clients, but for some reason I needed to access one of the mailboxes locally. They are all tied to system users so I just fired up alpine to deal with some overlarge attachment that didn't want to download. Alpine worked just fine I got the attachment, and was careful not to expungeor delete anything. When next the person looked at the account through IMAP though, their inbox was empty. The alpine client locally still sees all the emails, but they are invisible through IMAP. I tested and this happens upon any closing of the Alpine application. It would seem as though it performs PoP, but I can't see that anywhere, plus it's a local account. Edit: Just to clarify I'm talking about Alpine the mail client which is a successor to Pine. Not the distribution. Also I checked and for some reason the Alpine is moving (as Bodo suggested) the mail from /var/mail/user to /home/user/mbox or similar (the message dissappears quickly). It does not do the same thing for a different account I have on the same server where I do not believe I've made any changes though. Edit 2: So I figured out why the other account I had was not doing it. In particular the .pinerc (config file alpine apparently uses as a successor to pine) of the account where emails don't get moved when viewing has a line disable-these-drivers=mbox The thing is if I add this line to the account that does move mails, it loses access to the mails that have been moved. So I'm still not quite where I would like to be. Any idea what I might have set up wrongly?