This needs more information. Is this an IMAP account? Are message folders being stored on PC? How are you viewing to see the messages? Website? Are you viewing messages within Thunderbird, or looking at the profile from windows file explorer? With details, I feel this can be fixed.

The messages are from a variety of sources starting with Eudora as the email client. Note I am NOT retrieving the email from a mail server. It's not IMAP, POP, etc. These are complete old archived Email files going back decades.

The file(s) is stored locally on my Linux PC. It was brought over from my backup server (BSD).

All the messages were in a single email file however, Thunderbird started splitting the messages with headers in one file and the body in another. I'm not sure when that started and I can't find a way to put them back together. Thankfully, I have the original RFC-822 compliant files intact.

I place the email file(s) into the appropriate Thunderbird directory and open the local Thunderbird client. All the messages are in the Table of Contents pane. If you click on any message, the body is empty.

If I import the files, I get the same result -- all the messages are in the TOC but the bodies are empty.

Using the standard Unix/Linux mail command, I can view them but, of course, the mime content is just garbage and not rendered.

I hope this helps.

To see if they are, indeed, mbox formatted files for thunderbird, you can view the files for free at https://www.mbox-viewer.com/ that will confirm whether they are legit thunderbird layout. From my experience (and fuzzy memory), messages from Eudora need to be converted to mbox format. That must be done before Thunderbird can properly access them.

That conversion appears to be when Thunderbird, or the conversion separates the headers from the body. For years, I could access the messages using Thunderbird but then, something changed. I'll try some small files and see what it thinks.

The mbox-viewer works and the email are there from a single mbox file. Note that the header and body are retained together, unlike what happens in thunderbird.

The mbx file is readable in Linux using the mail command without errors.

Was Thunderbird displaying the messages properly until recently? What changed? Did you copy the message file into your profile again?

What makes you think that Thunderbird is splitting message data?

Into what directory do you put the message file? By simple copy?

How do you import it?

Have you tried repairing the folder in Thunderbird?

What conversion are you referring to? Thunderbird does not convert mbox files.

My guess is that the mbox file and index file became out of sync. Perhaps because of how you update the message file or get it into Thunderbird? If this is the case, all you have to do is right click on the folder in Thunderbird, select "Properties, then "Repair folder".

Another guess is that you think that Thunderbird is doing something to the message file because you're looking at the index file in the file system. No, that's just an index file.

All I know is that the original mbx file is ONE contiguous file. In Thunderbird, it gets turned into two files: 'name.msf' file which is small and a larger file 'name' with no extension.

Repair folder says No messages found although it's 233 MB in size.

The msf entry is just an index.

The answers to my questions might help us.

As I said: Another guess is that you think that Thunderbird is doing something to the message file because you're looking at the index file in the file system. No, that's just an index file.

Thunderbird is not splitting the message file.

All I know is that various other email clients from basic command-line mail can parse the mbx file without any problem. Thunderbird cannot. It used to be able to, but it no longer can. I don't go into these old messages very often so I have no idea when whatever changed happened.

I'll just quit using Thunderbird as a client for reading older mbx mail files as apparently, nobody has any idea what is going on. Thunderbird can display only the message index but not the respective messages any more.

The file contains 3584 messages and they're all complete using other clients. It would be nice to view them as a Local folder within Thunderbird like I used to but, apparently that is no longer possible.

I don't have the time to waste on this anymore. Thanks for trying and for the suggestions.

If the mbox file is well formed, there are other ways to get Thunderbird to display it properly. Come back if you are interested.

When you import an mbox into Thunderbird, it necessarily creates an index file so it can more quickly find messages during a search. Nothing is "split" - all header and body information is still intact in the main mbox file. I have some local folder with up to 4500 messages in them, some of them imported from other mail systems. Thunderbird deals gracefully with them.

"Mbox" format is not a well-defined standard. There are several variations that are not necessarily compatible with each other. You might want to check out this article for some insight:

https://en.wikipedia.org/wiki/Mbox

You might try the addon "ImportExportTools NG" which makes the process less manual and maybe less error-prone.

https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools-ng/

If interested, and don't mind sharing, I would be glad to further investigate this. You could send the mbox file to davidthunderbird at gmx dot com.

Sorry David, there is too much personal info in those email messages so I won't be sharing it. Thanks for offering thouigh.

I just regret we can't assist you. I've never encountered an mbox file that could be read by others, but not by Thunderbird. I do encourage a test using the above-mentioned importexporttools NG addon, as it might somehow 'fix' whatever is there. Just install it, highlight Local Folders, and rightclick and select the importexport option to import mbox. If you've previously tried to move that mbox file to to same Local Folders, be sure it's removed first.

David, part of the issue is that this mbox file containes more than just Internet addresses. It contains uucp, ARPA, Grapevine, Appletalk, Novell, XNS, mainframe, and other address formats. Many don't use the @ symbol in their structure. It is quite possible that this is what is causing Thunderbird to fail. Also note that Thunderbird used to handle these quite well but, after multiple upgrades, that capability was lost.

Should I infer then that this mbox file has never been accessed by Thunderbird? My assumption had been that Thunderbird had previously used it. Your comment implies that the file has possibly had multiple 'parents.' Thanks for the feedback.

The mbox file has been accessed by versions of Thunderbird in the past, but not in the past couple of years.