... and related to this, what is the recommended size for a Local Folder? I read here, http://kb.mozillazine.org/Limits_-_Thunderbird that it’s 4 GB and each of my Local Folders is well below this. Can someone confirm the size limit please?

Local Folders is a pseudo account that contains multiple folders. The 4GB limit is for each folder, not for "Local Folders" as a whole. The same limit applies to POP accounts.

The terminology can be confusing. Folders to store mail that you downloaded are stored locally on your hard disk, but they're not called local folders. That name is reserved for the "Local Folders" pseudo account.

"I noticed that Thunderbird stores all mails of one Local Folder in one single file which I can open for example as a text file. "

I suspect you're talking about a inbox folder storing all of the messages for that folder in a "inbox." mbox file. You can store messages in other folders in "Local Folders".

There are two basic storage formats. Mbox files (stores all of the messages for a folder in a single file) or maildir (stores each message as a separate file). The 4GB limit applies only to mbox files. Think of maildir as somewhat similar to Microsoft's .eml file format but coming from a UNIX heritage.

The Maildir support is not as mature as the Mbox support. I suggest you stick with the Mbox file format. They plan on adding a feature to let you convert between formats, though its unclear when that will be available.

‘The 4GB limit is for each folder, not for "Local Folders" as a whole. The same limit applies to POP accounts.’

Understood.

‘The terminology can be confusing. Folders to store mail that you downloaded are stored locally on your hard disk, but they're not called local folders. That name is reserved for the "Local Folders" pseudo account.

I meant the 'Local Folders' that are stored as C:\Users\MyName\AppData\Roaming\Thunderbird\Profiles\l5yq8b1p.default\Mail\Local Folders\Example Folder.sdb\etc .

Please advise if you meant something different.

‘"I noticed that Thunderbird stores all mails of one Local Folder in one single file which I can open for example as a text file. " I suspect you're talking about a inbox folder storing all of the messages for that folder in a "inbox." mbox file.’

No, I meant the Local Folders in the path C:\Users\MyName\AppData\Roaming\Thunderbird\Profiles\l5yq8b1p.default\Mail\Local Folders\Example Folder.sdb\etc

‘You can store messages in other folders in "Local Folders".’ Understood, that's what I'm doing.

‘There are two basic storage formats. Mbox files (stores all of the messages for a folder in a single file) or maildir (stores each message as a separate file). The 4GB limit applies only to mbox files. Think of maildir as somewhat similar to Microsoft's .eml file format but coming from a UNIX heritage.’

One clarification required: does 'Mbox' only apply to the Inbox or to the Local Folders, too?

‘The Maildir support is not as mature as the Mbox support. I suggest you stick with the Mbox file format. They plan on adding a feature to let you convert between formats, though its unclear when that will be available.’

That would be good and allow me to switch later.

There's no way I know of (as yet) to make Local Folders use maildir.

I think that in part that this is due to the way we are invited to make this decision when we set up an account. Since the Local Folders pseudo account is set up automatically we don't get this window of opportunity.

"One clarification required: does 'Mbox' only apply to the Inbox or to the Local Folders, too? "

It applies to all folders in "Local Folders".

There is an older way to specify you want to use maildir - set "mail.serverDefaultStoreContractID" to "@mozilla.org/msgstore/maildirstore;1" using the config editor. You can do that in a new profile before "Local Folders" is created as a side effect of adding your first account. I suspect that would work with "Local Folders" because I've seen bug reports mentioning maildir being used with "Local Folders".

https://wiki.mozilla.org/Thunderbird/Maildir

Dear tanstaafl and Zenos, Thanks for your reply. I think I under now that 'mbox' refers to 'Local Folders'. I assume I'll just stick with what I've got now as all mails are there. I just wanted to be prepared for the future, as I have used Outlook Express, then Outlook 2003(?) with .pst files, then Windows Live Mail and experienced significant problems each time I had to transfer my personal/local folders.

So Thunderbird seems a no-nonsense alternative and I hope I can use it for a long time to come! Best wishes Blackredgold1964

MBOX is the name of the file format this email are stored in. If you google the mbox file format you will find it is about as old as EML. This is because it is a stack of EML files one after the other.

Historically Mac mail and many other mail programs used mbox format, especially in the UNIX and Linux world (Macs OS is a UNIX derivative) .

But without going into any technicalities, Thunderbird has an add-on that can export your mail to EML. So all your concerns are for nothing really. https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/

Thanks, Matt, for the explanation. I too think, I'm safe now with the Local Folders, in case I need to change in future.

A message to all, Just out of interest, this thread mentioned a '"Local Folders" pseudo account' - I assume this 'pseudo' refers simply to the Local Folders that are stored on my c:\ drive.

I googled 'pseudo account' and still did not quite understand it - if someone could provide any further explanation or point me to some background info that would be useful.

Local Folders is referred to as an account, and it appears alongside all your other accounts in the settings page. I think Tanstaafl's advice would work, but you need to know to set this preference before running Thunderbird for the first time…

However, Local Folders differs from all the other accounts in that it does not connect to a server and it isn't associated with any particular email address or account; so it behaves like an account yet isn't the same as any of your "real" email accounts.

"Pseudo" is my own choice of description and isn't a description you'll find expanded on elsewhere. Perhaps I could call it a Quasi Account and cause even more confusion. Internally it is sometimes referred to as a "Special Account", which pops up when users try to delete it.

http://kb.mozillazine.org/Local_Folders

I usually try to throw in a mention of it being part of Thunderbird (hence the reference to "account") in order to be clear that we're not talking about the OS and its file system in general.

Hi Zenos,

Thanks again for the clarification and the link. I understand now - the 'pseudo account' are the 'Local Folders', that I can see in Tools - Account Settings.