Hi there, thank you very much for any help you may provide. Mac OS X 10.9.5 Latest version of Thunderbird. I created a fake account in Thunderbird in order to see Local Folders on the left Panel (otherwise the application does not create Local Folders in Profiles). I would like to import old emails, see them offline, as backup tool. So, I tried to import emails in Local Folders in 3 different ways : 1) Right click on Local Folders, select ImportExportTools NG, import MBOX file (then tried also the other options in this popup window), so select an MBOX file (from external disk). Finder does not stop at the level of MBOX, does not allow to select that but enters subdirectories, until reaching .emlx files. So I can select only .emlx files and once OPEN, system prompts " the file ...cannot be open because corrupted or not an MBOX file" !!!! Still the .emlx file appears in Local Folders tree on the left panel (GUI). 2) Copied manually MBOX (files/folders whatever with this extension!) into Thunderbird's Profiles' Mail 's Local Folders 's. Quit and so reopen Thunderbird. Other files are created into that Local Folder (e.g. nameof themboxfilechosen.msf) .... but when opening Thunderbird NOTHING is displayed, no messages appear there. Folders are correctly visualised on left panel, under tree Local Folder, however messages are not there. 3) Used the native IMPORT menu from Thunderbird, without using ImportExportTools NG. Tools -> Import -> Mail , so I select Apple Mail. It runs 1 sec and returns the message that no mailboxes are found in Mail.... so it does not import anything yet. Even in this case I worked offline. And Mail application was closed. So, the import fails with all 3 methods. Should I rename extension of MBOX files/folders !? I really do not know what else to try, and would need to see my emails here, offline. (Apple Mail download and manage as IMAP, Thunderbird kept as backup emails browsers, to be used offline only). Thanks much for your any support!