I have been using Thunderbird software to manage my e-mail for several years. My "underlying" e-mail account is a Yahoo e-mail account, because my ISP is AT&T. On my old computer, which was a Dell Inspiron 3646, once an e-mail was in my Thunderbird IN box, it stayed there until I deleted it or removed it to an e-mail file in Thunderbird. Periodically, I simply went into the Yahoo account and deleted everything from the IN box, as well as from Sent, Spam and Trash. Even though I had deleted an e-mail from the IN box in the Yahoo account, that e-mail would stay in the IN box in the Thunderbird account, even if I closed Thunderbird and re-opened it. Now I have a new Dell IPS 8940 computer. E-mails go from the Yahoo IN box to the Thunderbird IN box, as they have in the past. If I then go into the Yahoo IN box and delete the e-mails, they will only stay in the Thunderbird IN box as long as Thunderbird is open. If I close Thunderbird, and then reopen it, e-mails that were in the Thunderbird IN box before I closed it are gone from the IN box, if I deleted them from the Yahoo IN box prior to closing Thunderbird. Is there something I need to set in Thunderbird so that e-mails will stay in the Thunderbird IN box until I actually move them out of the Thunderbird IN box, or delete them in Thunderbird? I would like to be able to delete e-mails from the Yahoo IN box, and have them remain in the Thunderbird IN box, even after I close and then re-open Thunderbird. That is how the system has always worked in the past. Thank you. Connie Yanicka