Despite your desire, the MSF file is a database of mail in the folder including informnation about when the folder was polled last among other things.

So the short answer is no!

The long answer is still no! But to also question why would you back those files up anyway. If you delete them, Thunderbird will simply recreate them. In very rare cases where the mail server does not support tags, you would lose them if the file was deleted. But I really see no other downside other than the file being recreated on access slowing the program while it does that.

The same goes for IMAP mail folders. As all the mail is on the server, if you deleted the mail stored in those folders, Thunderbird would simple re download them post haste when the folder is selected in the user interface. They serve no archival purpose as anything in the backup that is subsequently removed from the server will simply be synchronized into oblivion if the backup were to be restored to bring the folder into line with the canonical source (the server).

Despite your desire, the MSF file is a database of mail in the folder including informnation about when the folder was polled last among other things. So the short answer is no!

I did not know this. It means that "data" and "metadata" are mixed in the same file, right? This is usually a bad practice (for several reasons, but this is probably not the place to discuss it) and leads to several issues; like the one presented in this thread, where there are no changes in the data but you are forced to handle billions of bytes just for a change of a few bytes in the metadata. But I am going off-topic here...

Since it seems that MSF files could not solve this problem, can you save the mailbox data and emails into a different format in Thunderbird?

It would be great to use a standard format (like EML/MBOX) and not a proprietary one (MSF). Please note that you can easily synchronise/backup a format like EML (since each email is stored in a different file) and you would not suffer the problem mentioned in this thread.

I think the other points raised by Matt are off-topic here, but I will provide some shorts comments below (and I will be happy to discuss them further in other threads).

OFF-TOPIC

The long answer is still no! But to also question why would you back those files up anyway. If you delete them, Thunderbird will simply recreate them. In very rare cases where the mail server does not support tags, you would lose them if the file was deleted. But I really see no other downside other than the file being recreated on access slowing the program while it does that. The same goes for IMAP mail folders. As all the mail is on the server, if you deleted the mail stored in those folders, Thunderbird would simple re download them post haste when the folder is selected in the user interface. They serve no archival purpose as anything in the backup that is subsequently removed from the server will simply be synchronized into oblivion if the backup were to be restored to bring the folder into line with the canonical source (the server).

I believe we have different views on this (and it is fine), but I think you must always have different backups of your data (even emails). Therefore, even if they are stored in a server somewhere "on the Internet", I think you have to keep (at least) a different copy of them. There are several reasons why this is a good practice, and I would be happy to discuss them, but I think we should do it in a different thread.

And it is not true that "They serve no archival purpose" since if the server gets destroyed or you no longer have access to it, you can still open all the emails (that you have locally). Obviously, this is also valid when you are not connected to the Internet.

Matt said

Despite your desire, the MSF file is a database of mail in the folder including information about when the folder was polled last among other things. So the short answer is no!

I did not know this. It means that "data" and "metadata" are mixed in the same file, right?

That would depend on your definition of data and metadata. As the index file, like just about every database index since DBASE contains certain information that makes locating the data in question fast. In this case the MSF is a mini database that has an offset entry into the MBOX file for the actual email, or the server reference (depending if the data is actually stored locally at all) and other information for populating the user interface without referencing the actual gigabytes of data in the MBOX files. I would consider the MSF to therefore be metadata.

Essentially the MSF is the same as the message header, except it does not contain all of the header. I am told by many governments this is "MetaData" and clearly it is not encrypted in the s/Mime specification leaving me to consider they may be correct. Either way It is not information that needs to be backed up in my opinion as deleting the file will see it recreated on the fly.

This is usually a bad practice (for several reasons, but this is probably not the place to discuss it) and leads to several issues; like the one presented in this thread, where there are no changes in the data but you are forced to handle billions of bytes just for a change of a few bytes in the metadata. But I am going off-topic here...

You are, and as you suggest. I disagree with you here. Needless to say, there are moves to modernize this part of the program that was inherited from Netscape all those years ago. Bug https://bugzilla.mozilla.org/show_bug.cgi?id=1572000 But as the MSF serves no purpose in an archive, it may contain information about the email. But it does not contain the email. That the MBOX file if it is stored locally.

Since it seems that MSF files could not solve this problem, can you save the mailbox data and emails into a different format in Thunderbird?

I really have no idea exactly what that means. Sorry. The MSF file is an index/database to populate the user interface.

It would be great to use a standard format (like EML/MBOX) and not a proprietary one (MSF).

The MSF (or MORK format database) is an index into the MBOX store of local email for the folder. It is also doomed. See this meta bug for the project https://bugzilla.mozilla.org/show_bug.cgi?id=453975

Please note that you can easily synchronise/backup a format like EML (since each email is stored in a different file) and you would not suffer the problem mentioned in this thread.

Yes you would. as the MSF is a meta data index not the data itself. Even the maildir like storage that has been turned off for most of the last decade uses an MSF index file. https://support.mozilla.org/en-US/kb/maildir-thunderbird </blockquote>

I think the other points raised by Matt are off-topic here, but I will provide some shorts comments below (and I will be happy to discuss them further in other threads).

OFF-TOPIC

The long answer is still no! But to also question why would you back those files up anyway. If you delete them, Thunderbird will simply recreate them. In very rare cases where the mail server does not support tags, you would lose them if the file was deleted. But I really see no other downside other than the file being recreated on access slowing the program while it does that. The same goes for IMAP mail folders. As all the mail is on the server, if you deleted the mail stored in those folders, Thunderbird would simple re download them post haste when the folder is selected in the user interface. They serve no archival purpose as anything in the backup that is subsequently removed from the server will simply be synchronized into oblivion if the backup were to be restored to bring the folder into line with the canonical source (the server).

I believe we have different views on this (and it is fine), but I think you must always have different backups of your data (even emails). Therefore, even if they are stored in a server somewhere "on the Internet", I think you have to keep (at least) a different copy of them. </blockquote> That does not explain any reason to keep an MSF file, the whole crux of your original question. It is meta data that if deleted will be recreated on the next sync of the folder.

There are several reasons why this is a good practice, and I would be happy to discuss them, but I think we should do it in a different thread. And it is not true that "They serve no archival purpose" since if the server gets destroyed or you no longer have access to it, you can still open all the emails (that you have locally). Obviously, this is also valid when you are not connected to the Internet.

And the MSF files still serve no archival purpose. They serve no purpose even if deleted as Thunderbird just recreates them.

Restoring your carefully crafted backup of a Thunderbird imap account is a task destined for failure. The local storage part of Thunderbird IMAP account is designed to be little more than a local cache to speed up display. Restore the data, attempt to go online and all your mail and folders will be deleted because they don't match up to the canonical source (the server). Just search this forum for all the disappointed folk that have already tried to restore the IMAP backups for their closed accounts. Try and save them as EML files offline and you get it trying to validate the data by going online. SO the backups are really somewhat useless.

You might think these things are off topic. I would think they would be quite important to someone making backups that they can not restore should the data actually be lost. HOwever you can say it is off topic and ignore the elephant if you like.

There is, as far as I am concerned only one sure way to make a backup, and that is use the import export tools addon to actually export each folder to EML or MBOX outside of Thunderbird. This is slow as the addon verifies each mail with the servewr on export. However it does export them. Which the profile export on the tools menu does not do. It relies on being able to connect to the server and download the IMAP mail again.

I apologise, I made a mistake in my first message, which caused lots of misunderstandings in the subsequent messages.

When writing my first message, I was simply referring to "the files in the ImapMail folder" (that is what I see when I do my backups). Then, to clarify the message and provide more details, I opened that folder to specify better the filenames/extensions. I do not know why, but I somehow was unable to correctly follow the line and I read the wrong one. In the ImapMail folder, for each folder in my email account, I have two files: one with the msf extension and one without any extension. One of them is usually big, the other one is much smaller. I made a mistake and, probably reading the wrong line, I thought that the big ones were the ones with msf extension, but this was wrong (the big ones are the ones without any extensions).

After reading your last message, I understood that there was some misunderstanding, so I went to check the files again, and I noticed my mistake. I truly apologise for that.

Therefore, all I said above refers to those files without extension and not to the msf files.

Going back to my original questions:

Is there a way to tell Thunderbird to change those files only if I received new emails in the folders they memorise? btw, why do those files change if there are no new emails?

Do you have any suggestions on them?

Thanks

Is there a way to tell Thunderbird to change those files only if I received new emails in the folders they memorise? btw, why do those files change if there are no new emails?

"those files" refers to the files used by Thunderbird to store emails.

Doesn't anyone have any ideas about this?

It is really annoying that those files are modified even if there are no new emails.

Please let me know if I need to open another question since this one might be confusing due to the mistype in my first message.