When pulling in mail messages, Confluence displays the "Date" as the date the message was pulled in from the POP store, or possibly the date the message was put into the POP store. It should display the date the message was sent.

I'm using a personal space in Confluence to archive important messages; I don't always drop these messages into the confluence-accessable POP store on the day the message was sent. In this case, Confluence shows the date I put the message into the POP store.