I take it you set up this gmail account in Thunderbird? You can just drag-and drop (or better, select, '''right-click,|Move to''') between folders, even when the folders are in different accounts. And if you didn't set up the gmail account in Thunderbird, then the unexpected movement of messages has nothing to do with Thunderbird. Posting your settings here ''may'' help someone work out what has happened. F1 (Help), Troubleshooting Information. Clear "Include account names" Click on "Copy text to clipboard" Paste into your reply (ctrl+v). Check it over for anything you'd rather not share. But we need to see server names. I'm asking you to do this because, in reality, there is no such thing as a "Thunderbird account", but we have a pretty good idea what you mean. The information I'm asking for will clarify this.