mozmsgs folders contains basically EML versions of your mail. Minus any attachments. Their sole purpose is to allow windows search to search your mail. Personally I tuned the option off years ago, deleted the 150,000 files in the folders and reduced the size of my profile by about half. I don't use windows search for that anyway. Brain dead rubbish IMO.

In the root of each folder. Say.Mail/LocalFolders/ you will see a file inbox and an accompanying file with the same name with an MIF file. The file with NO extension is your actual mail and by itself represents a valid backup of all mail in that folder. You will have one file to represent each folder that appears in Thunderbird. If you have a sub folder in Thunderbird it will appear in the file system with an SDB extension. So you could have inbox, inbox.msf and inbox sdb is infox had sub folders.

Mail is stored in the mail store folder in what is called the Berkley variant of the MBOX RD format. For us that translates to a text file with one EML file stored after another in the same file. Nothing technical at all really and it can be opened in Notepad (or a better text editor if it is really large)

So I think what I am saying is don't waste your backup space with mozmsg files. They add nothing to your experience.

Thanks for that explanation. I just want to make sure I understand completely before I start changing my backup procedures You wrote:

mozmsgs folders contains basically EML versions of your mail. Minus any attachments. Their sole purpose is to allow windows search to search your mail.

I use the search function in TB constantly to find stuff. If I were to not include those files in my backup, would this search feature still function if I needed to restore a backup?

Also, attached is an picture (in 3 images) of my mail/local folders/sent history directory. Let's take, for example, the year 2003. If I understand you correctly:

The file 2003 (with no extension): I should backup; this is the file with the actual mail in it The file 2003.msf: I should backup The folder 2003.mozmsgs: I don't need to backup if I don't care about the windows search function

Is that correct?

Thanks for your help.

To repeat. the contents of mozmsgs are there ONLY to help Windows search. Thunderbird has no use for them. You won't see these folders in Linux or Mac installations of Thunderbird. But you can check for yourself; move or rename them, in situ and see what happens.

You don't need to backup msf files; they are indexes and will be recreated as needed. Preserving them may make access to their contents a bit faster, but I think that's moot; to USE these backups you'd have to re-import them into Thunderbird and in doing so they would be re-indexed anyway.

I'd just backup the whole profile rather than cherry-picking specific files. If you start selecting particular files you need to be darn sure what you need. I don't have quite the time or motivation to work all that out.

The Thunderbird search index is the global-messages-db.sqlite file and this also is regenerated when it is deleted, so there is no need to back it up. So no relationship to the mozmsg folders or the thousands of useless files they contain.

To Zenos: I am having trouble transferring these files around due to their size. To be honest, this is not a backup issue. I mainly use a PC for my email but I have a Macbook Air that I use when I travel. I need to be able to transfer these local folders from my PC to the Mac every couple of months. Whenever I do that, I run into all sorts of problems because the profile file is so large. So, I have resorted to a workaround which just transfers the local folders which have been changed on the PC since the last transfer. It was going through this updating process that I noticed the discrepancy.

To Matt: Thanks. I won't worry about transferring the mozmsgs files then.