re : old Outlook .dbx emails I have imported the old .dbx emails files and later through an IMAP account I copied them into the mail server SUCCESSFULLY!

So all .dbx is ok.

re: and older .sdb emails? Outlook Express used .dbx. So what email client program was using .sbd ?

Are the .sbd files really 'folders' not files ? Open the .sbd folder what do you see in contents? Do you see mbox files - they have a name but no extension or may have .mbox extension ? Do you see index files which would have a .msf extension ? Post an image to help explain what you are seeing.

Yes, all .dbx are ok! The .sbd should be used by an older version of outlook express around 1998-2000. The .sbd are folders and there is in the same directory the name of the .sbd directory without extension. Opening a .sbd I see other .sbd directories (the subdirectories in the e-mail client) and the name of the .sbd directory without extension. I'm not so sure that the files without extension are .mbox files but it's possible to open them in text format with gedit and read in a quite way the e-mails contents (unless the attachments). Now I attach some images of the .sbd directories and files... Thank you

Back in 1998 Outlook Express 4 used .mbx files, which are a form of mbox file. So in your case, the file format of files with no extension are .mbx type.

When a folder has subfolders, this creates the .sbd folder of same name. This is the same in Thunderbird. So for Thunderbird to know about the subfolders contained in eg: Dario folder, there has to be a Dario (no extension) mbox file and a Dario.sbd folder which would contain emails in mbox files. In OE , the .snm appears to be indexing file which in Thunderbird is .msf file.

As the .mbx files are a type of mbox file have you tried to copy paste one of them into 'Local Folders' ? Try this test and report back on result.

Exit Thunderbird. Access profile folder. The default location is: C:\Users\<Windows user name>\AppData\Roaming\Thunderbird\Profiles\<Profile name>\ Mail\'Local Folders' Copy (not move) and Paste an mbx file (one you have opened using gedit to confirm it has emails) eg: into 'Local Folders' folder.

Start Thunderbird Look in Local Folders mail account. Do you see that folder ?

Before you copy and paste, Make sure the OE files with no extension really have no extension. You need to make sure you do not hide folder extensions. If you after checking you cannot see .mbx then it's ok. It is important that in Thunderbird there really is no extension for mbox files. If necessary you can remove any extension by renaming.

https://support.microsoft.com/en-us/help/4028316/windows-view-hidden-files-and-folders-in-windows-10 https://www.thewindowsclub.com/show-file-extensions-in-windows

It works! Thank Toad-Hall

That's good to hear. Continue to use the copy paste method to put .mbx files into the profile 'Local Folders' whilst Thunderbird is closed.

Dear Toad-Hall, now I have the last, I hope, importing problem. In fact I have .nsf files of old emails of Lotus Notes. I've tried to search a solution in internet but I've found the same systools of the previous discussion and another German tool that in the demo version tool were not able to import nothing in Thunderbird. In Win 10 I have installed Outlook 2019 retail, the demo version, that is working until Sunday 24 November (tomorrow) then I've imported some .pst files of old e-mails. Let me know if it could be useful to import .nsf files. Thank you

If you can get your hands on Lotus Notes then the conversion to Outlook pst is possible. A useful discussion here: https://social.technet.microsoft.com/Forums/ie/en-US/65fcf2b1-9308-4127-b98b-f0fb3ae0da7d/how-to-convert-nsf-to-pst-without-lotus-notes-installed?forum=officesetupdeploylegacy

then you could export emails as .eml files which can be imported into thunderbird using 'ImportExportTools NG' addon.

Otherwise you would need a converter in which case you may as well convert .nsf into mbox files.

But, in all cases, I would recommend you make backup copies of the .nsf files just in case some corruption occurs.

A link in this post points to an nsf-mbox converter with a 30-day trial:

https://www.spikevare.com/lotus-notes/thunderbird/

There are many other commercial products that offer limited trial versions.

Dear Toad-Hall and sfhowes, I've tried with Lotus Notes Client 8.0.2 that opened some .nsf files: - <myaccountname>.nsf; - busytime.nsf; - favorites.nsf. But, in the first, my account, I have had a surprise in fact there was only the structure of the e-mails that is directories and subdirectories. Unfortunately, if you don't have another idea, I suppose that e-mails are remained in the company server. By now... Thank you and kind regards. Fabrizio