You might try right clicking the account in the folder pane and selecting settings from the menu and looking over your settings, but I am not aware of any automatic deletions. Having said that such could be implemented with an addon and likewise a defective one could just move things to the trash. Mostly in the past such problematical items have come with anti virus / Security packages and purport to do things with spam or scam emails.

Thanks Matt, I have searched all over for a rogue setting with no luck.

It's funny because I also have Thunderbird installed on a machine at my home, with no issues?

Jeff

look for scam, phishing and spam detection setting in your anti virus product and turn them off to see if they might be affecting things.

Turn off anything related to mail again see if it helps.