This has happened to me twice now. I do not delete emails from purchases until the item is received. I leave it in my inbox and often will mark it unread. I went into it yesterday to check to see when I should receive a certain item and the email is gone. I have looked in all folders (spam, trash, archive, all mail) and it is not there. I blamed G-mail originally but now wonder if it is Thunderbird and if there is some way to retrieve it. Is there a defunct setting somewhere that I do not know about or understand? I have plenty of storage. Can someone answer this for me?