My grandmother uses Incredimail on her computers to check her email. She uses POP3, so when one computer downloads a mail message, it is not available on other computers. This causes a problem because, if instances of Incredimail are running on multiple computers at the same time, you don't know which computer has the email messages.
While I was down there, I figured I would switch the configuration to IMAP to help alleviate these problems. This is the situation where IMAP is supposed to work. I set up Incredimail to use IMAP, but the same behavior was happening.
It looks like Incredimail doesn't implement IMAP correctly. It doesn't synchronize the IMAP folders, but instead just downloads the messages, while leaving them on the server. I don't think that Incredimail should even state that it supports IMAP.