I do not see those folders as being related to the windows file explorer. I can not replicate that in the new outlook, this is about as close as I can get <img src=https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2025-02-09-07-37-48-83dd7d.png> So I fired up my outlook365, and waited about 10 minutes for it to retrieve or load of whatever it does with my mailbox settings. I can replicate it in the classic outlook, but it is folders hanging under the only account I have configured, not any local f0olders on the hard drive of my computer that would show up in the windows file explorer. <img src=https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2025-02-09-07-43-37-dc66e0.png> SO have got that far, Thunderbird does have a special account called local folders to which you can move emails to be stored on the local machine, independent of the account the mail was received on. Those will appear in Thunderbird as folders, but you will not see them as such in the windows file explorer, just as you did not see the outlook folders there.