How to create multiple "Local Folders", to have smaller 'mail_data.dat' files to backup

I moved from Outlook to Thunderbird because I liked it’s “one folder/one file” storage policy. eMClient looks great, but I now have a 7Go ‘mail_data.dat’ in my ‘Local Folders’ directory, which is a real pain to backup : my backup software can’t do a differential backup with just one big fat file, so the 7Go file is copied everyday.
I thought I could create multiple storage files like .pst in Outlook to reduce the amount of data to backup (one big ‘archives’ file which whouldn’t change often, and smaller ‘working’ files), but I can’t find out how to create another “Local Folder”.
Is there a solution ?

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In eM Client terminology Local Folders refers to the folder structure within eM Client. So you have Local Folders, and you have online folders. Each set of folders contains Inbox, Sent, Trash etc. You can only have one set of Local Folders, but a separate set of folders for each IMAP/Exchange or POP3 account.
It does not refer to a Windows directory structure.

You can have separate databases, but unlike pst files, you can only access one at a time, and you will need to restart eM Client if you change to a different one.

To do a backup using a third party application, you need to close eM Client, then backup the complete database directory. If eM Client is running during the backup, you will get empty files that are not worth anything. You cannot use an incremental or differential backup; it needs to be a full backup. You also can’t use a cloud backup option like Carbonite unless it only syncs when eM Client is closed. 

eM Client’s own backup facility will backup the complete database to a single zip file in the background while the application is running. The automatic backup will also run in the background, or even if eM Client is not running at the scheduled time.

Hello Gary,

Thanks to your answer I found a way to reduce the size of eM Client files !

I just created some fake POP accounts (by skipping the test results) to get new eM Client folder structure / Windows directories structures, where I can put my very old emails archives (that I just backup when I add archives, because they don’t change much), and I use the “Local Folders” to temporary archive emails that I don’t need on my IMAP server, and I can back it up everyday without having gigs of data.

So thank you very much !

Best regards,


Interesting solution. :slight_smile:

Hello all, 
still no intention to implement a method to divide this unique gigantic file, like Outlook with PST files? All the folders and emails in one only file is too much dangerous and highly inefficient for any backup strategy.

I think you got it the wrong way around. eM Client does not use one file; there are more than 200 of them that make up the database. Each message folder and section like contacts etc have their own individual files within the database. This is a lot safer than the Redmond Team’s single storage file. Sure you can have multiple pst files, but essentially everything is in one file. If that pst becomes corrupt - so sad. At least with eM Client, it is possible to recover data if one of the individual files becomes corrupt.

Fortunately eM Client also provides a configurable automatic back feature for when you store your data in Local Folders. Just set it and forget it. It will automatically backup even while the application is in use, and conserve disk space by removing older backups as you go. You should be using the integrated backup anyway, even if your data is stored on your  message server. All in all a very efficient backup strategy.

Ehm, no. I see something like 18 files every account, the main data files are the 4 *.dat (mail_index.dat conversations.dat mail_data.dat and mail_fti.dat)

If i have the same account from the year 2000 until today, 19 years of email are HUGE for 4 files, AND every new email change the whole archive because all the 19 years are on the same set of file.
So, my backup see gigabytes of files to backup every time i do a backup.
I repeat: i receive ONE email today, the WHOLE archive change, so the backup must copy 19 years of data for ONE ONLY email received TODAY.

Logic would like i was able to have different files (or a different set of files) based on my archiving method, for example by year (or folders).
So, 19 years of email could be 19 files or set of files, and if i receive ONE email today, 18 already-backupped database files remain untouched and without any need to be backupped again (and again, and again, every single email received).

In eM Client, your Inbox and Archive are NOT the same files or directories on your disk.

But let’s look at MS Outlook. You have a pst file and you receive a new message. It will be incorporated in that single file. So how is this a better system than eM Client, in which there are multiple files for the message store? The archive and the Inbox are separate directories on your disk, so receiving a new message does not alter the Archive folder at all. The local folders and the IMAP cache are separate directories on your disk. This is not so with MS Outlook.

trying to figure this out too. Been using Outlook with 9 email accounts. Each has it’s own .pst file to keep the files as small as possible. Can you do the same in eM ?

Well, they are not the same application to begin with. eM Client is a SQL database, and MS Outlook is not. They save data in different formats.

SQL is actually a much safer option as it does not edit the data file directly. It modifies the data in a wal file, and later writes that data back to the dat file. 

In eM Client, each email account has it’s own directory and files. By default MS Outlook only has one file. Very dangerous!

I’m using 11 .pst files in outlook. I just imported into eM. The mail_data.dat file is 6.3GB. Is that a average file size for you guys?

No such thing as average, unfortunately. But by default email accounts are setup in eM Client as IMAP, and only the headers are downloaded. So in that case the file will be very small, regardless of how many messages are there. But if the data is stored locally, in Local Folders, or cached like when the IMAP account is configured for offline use, then the full message and attachments will be in the database. So then it will be much larger. 

Forget it, they don’t want to listen to reasons. Last reply to me was “Mario, I honestly don’t think you know what you are talking about.”

Think your comment got cut off Mario. "Ooook"means?

What’s eM’s approach to long term data file management? Love to learn.

I remember it was not so long ago that by default email clients stored data locally, and there were so many addons and other applications for backup and syncing of that data. But now it seems everyone stores their data on the server and leaves the management of that data up to the provider. Certainly makes sense when you have many devices accessing the same data, that a central management point would be the server that they are all connected to.

You can certainly see hints of this in eM Client where the default account setup is IMAP, and offline caching of data is not enabled. I was reading recently where in the upcoming version 8 there will be server searching available for the first time. So no need to locally cache anything, right? There are also new features like cloud storage support for attachments. Looks like the local database will just be getting smaller and smaller.

But eM Client also has an excellent automatic backup feature for long-term management of locally stored data if, like me, that is your preference.