Comment 8 for bug 365270

There is nothing wrong with Evolution. The behaviour is expected in an imap mail client. The "Trash" folder isn't actually a folder, but simply lists email that has the "deleted" flag set. When you move an email from Folder A to Folder B, a copy is made into Folder B and, if successful, the original mail gets the "deleted" flag set. In order to permanently erase the original message, an expunge command needs to be issued with Folder/Expunge. See RFC 3501.

In any case, this is not a security issue.