So I have some good news and some bad news for you. Normally this is where I ask someone which they want first, and then give it to them in the reverse order to highlight that the order is meaningless when there's nothing to advocate for, so let's get started.

You're not incorrect that the msf file is the index file of the pair of files used to store the contents of each mail folder, and that parsing it into a usable format would provide you with a listing of the messages that were there, minus their contents. The file structure is known as Mork and has been in use for almost 20 years, dating back all the way to the Netscape days, which would tend to suggest some hope that there was a well-travelled path to making it happen. And that's where the bad news arrives...

Mork has been decried for almost as long as its been in use for being an example of bad practices in information storage. It's unnecessarily complicated and internally inconsistent, obeying a mishmash of rules from several different languages, and even then only when it sees fit to. At least that's what I've heard from several people I respect, this lies well outside my bailiwick and nothing I'm saying should be taken as gospel.

To that end, I'm going to point you to the only tool I'm aware of that actually tackles a situation when you're attempting to parse just the index file as opposed to the more common goal of converting the pair of files into the constituent .eml files they're meant to contain. It has the benefit of having a well written readme file which adequately explains the inherent limitations and what you can realistically expect for the effort.

I wish you well, and if you find something that works better, please share it here so I can learn something too.

mork-converter.py

Thanks so much for the information! The mork converter is a bit too convoluted for my purposes so I guess whatever emails I received in the two missing months will have to remain a mystery. I know I shouldn't complain about Thunderbird when it's free but I think it may be time to seek out a more modern email client.

Thanks again!

You can do a fair bit of useful extraction using a decent editor with a regular expression capability. At the very least you can extract all the lines containing an @ and therefore presumably an email address. There is a nuisance in that some email addresses become wrapped to the next line.

Thanks Zenos. That's all a bit over my head I'm afraid so I'll just have to hope nobody sent me anything important during the missing time frame.

Had an idea.... Sometimes people have 'Inbox.msf' files that are out of sync with the actual contents of Inbox mbox file. In this instance, they may be seeing headers of emails that may not exist. Perhaps you could create the same senario in reverse to force a view of missing email headers.

Close Thunderbird. Create a backup of current 'profile name' folder, if not already done.

Access profile folders, delete the good 'Inbox.msf' file and paste in the rescued 'Inbox.msf' file. Start Thunderbird and see if the rescued 'Inbox.msf' shows the headers of the emails that no longer exist.

If this works then you can copy the info manually or create screen dumps of headers to create images for reference.

Then you can simply access the Profile folder and delete the bad Inbox.msf, restart Thunderbird and a new good will be created and all will be back to normal.

Toad-Hall, thanks for the suggestion but that didn't work. I think it rebuilds the .msf file when you go into an inbox so it just rebuilt with the emails that were there rather than telling me what was missing. Thanks for the suggestion!