When you have a mail folder that is 20G and you delete19G of messages, you would think that the file should be only 1G. But, if you check properties, you will find that the folder is still 20G. Even if you close/reopen the program or reboot the computer.

http://kb.mozillazine.org/Deleting_messages_in_IMAP_accounts

When you delete a message, it is only marked for deletion in an index file, the actual message is still in the file until you clean out the garbage. This happens when you 'Compact' the file, it actually rebuilds it and removes all the deleted messages. Now that file shows 1G used.

You should be able to take your oldest messages and archive them and then transfer the files to a thumb drive. I assume you have a USB port available.

Archive them in smaller chunks (say 100M each) that are easy to identify and small enough to load back into a non-monitored folder if you ever have need of the messages.

It is your mail, and only you know which mail is important. Or the logical way to save it. By date, by client, by subject, etc.

TB-38.2 Win10-PC

Thanks Gild - much appreciated. I'd forgotten about compacting.

When you suggest archiving the older messages, could you please be a bit more specific about what you're suggesting? Ie, would I use the Archive folder within my work mail account, or would I use a folder in Local Folders? Either way, how do copy them out of these places? Do I use the TB Export function, or do I copy from a subfolder in the mail profile? After I've done that, do I just delete the messages from within TB and then compact what's left?

Any email you store in a 'Local Folders' mail account folder is stored on your computer in your profile folder name 'Local Folders' mail account. You can view them at any time; they are not stored on the server. I would also recommend a backup of any emails you keep only stored in one place.

Option 1: You could use create suitably named folders in Local Folders and simply use the right click 'Copy to' option.

Option 2: Create an 'Archives' folder in Local Folders' and set up Archiving to point to that folder.

Option 1 info: After synchronising your subscribed folders so that you have an up to date copy in Thunderbird, go into 'offline' mode to stop further synchronising.

Create suitable folders in 'Local Folders' mail account. Highlight emails, right click on highlighted emails and use the 'Copy to' option and select suitable folder in Local Folders. Check you can open and read emails ok to confirm they have been copied ok. Then select the imap mail account folder and delete the emails you 'copied' to Local Folders. Compact the folder. Go to online mode and your folder should synchronise with server removing all those emails you deleted from imap mail account, off the server.

Option 2 info: Create a new 'Archives' folder in 'Local Folders'. Then Set up Account Settings.

'Tools' > 'Account Settings' > 'Copies & Folders' for imap mail account. Under 'Message Archives' section. select: 'Keep message archives in' Select: 'Other' and the 'Archives' folder on 'Local Folders' click on 'Archive Options' button

Depending upon how you want to store messages and how many emails you get on a monthly basis you have some options. I have quite a lot of emails per month, so I choose 'Monthly' option. I select the option to keep folder structure, so if I'm archiving my 'Sent' folder, I would like to see a 'Sent' folder in my Archived email folder. click on OK. then click on OK to save and close Account settings.

Go offline to stop synchronising folder. Test: select one email so you can see it in the Message Pane. click on 'Archive' button. check the Archives folder in Local Folders. Depending upon the folder name it was stored under- that folder name should appear in the month folder. Still in 'offline ' mode select that archived email to confirm you can read it. In the example I've shown Inbox and Sent.

If you selected the same archive options as me, you could see something like this example: Local Folders >> Archives >> >> 2015 >> >> >> 2015-01 >> >> >> >> Inbox >> >> >> >> Sent

This should keep emails in small organised files that are easy to access and easy to create backups. It should remove the email from the original imap folder.

Remember to compact folders after deleting several emails. Remember to backup your emails - do this in offline mode. You could backup your entire Profile folder name or mbox files or individual emails in .eml format.

Once you have moved emails into Local Folders and removed them off the server, you could perform a backup.

• http://kb.mozillazine.org/Profile_backup

You can access profile folders and copy the profile folder name. In thunderbird: Help > Troubleshooting Information clickon 'show folder' button This will show you the contents of your profile folder name. Close thunderbird now - this is important.

Go up directory to copy the profile folder name folder usually called xxxxxxxx.default, where the x's are letters and numbers.

if you cannot see files and folders then make hidden files and folders visible:

• http://kb.mozillazine.org/Show_hidden_files_and_folders

More info on where you profile is stored:

• http://kb.mozillazine.org/Profile_folder_-_Thunderbird

After backing up restart Thunderbird.

There is also a great addon tool which allows you export mbox files as a backup of just folder or export as individual .eml files which you open. ImportExporttools:

• https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/

Download the .xpi file to desktop or downloads folder.

In thunderbird: 'Tools' > 'Addons' OR 'menu icon' > 'Addons'

click on gear wheel icon and select 'Install addon from file' locate the .xpi file you downloaded and click on Open Restart Thunderbird.

To export a folder as an mbox file: Right click on folder and select: ImportExporttools > Export folder

To export emails as individual .eml files. Right click on folder and select: ImportExporttools > Export all messages in folder > EML format

Another issue the OP has, is the capacity of the SSD on his laptop. He cannot simply move the files to Local Folders. He has to remove them from his hard drive to free up space.

I suggest that he 'archive' or transfer the older files in small chunks to an new created unsynchronized folder, under 'Local Folders', then transfer it to a separate memory storage device, like a USB drive. (They are available in USB2, [or USB3, if his laptop supports that standard]. and come with large storage capacities.) His USB drive will contain the files in Thunderbird's native format, mbox.

He could put many, or all, of his archived mail files on that single drive.

His problem will be how to determine which file contains the message(s) that he wishes to review. This may determine the way they should be grouped.

He only wants to load a minimum number of messages to avoid exceeding his SSD capacity

When he needs the messages, he loads the correct 'file' back into Thunderbird using an unsynchronized folder. Use Thunderbird to process the mail, and then save it to his regular folders.

If he saves new mail into the 'archived' USB copy, it may make it more difficult to find recent messages.

The USB stick will still contain the 'archived' messages. Do not forget to backup the files on the USB stick to prevent a catastophic loss, if the stick becomes lost or corrupt.

TB-38.2 Win10-PC

Additional clarity:

All folders in 'Local Folders' are not synchronised. Suggested two methods to put emails in Local Folders, but I would prefer the archive option as it auto sorts by date.

Once in 'Local Folders' - I suggested backup methods. Backup the whole profile folder and store externally, but of course would be to any place the user desired except for within a thunderbird mail account.

By using the 'Archives options' all mail is auto sorted by year and month, so after backing up, the OP has a choice of making an extra copy of a mbox file which can be reimported as required or creating .eml files fo those very old emails.

All backup and copies of mbox files or .eml files will prompt to ask for where to store them - so obviously you would choose an external storage device - I did not think I needed to make it explicit that when making a backup of any type, you need to choose where to put the backup. But for clarity - you need to choose where to put all backed files. Suggest you use an external storage device just in case of computer failure or issue with disc space.

Once in 'Local Folders' and all is backed up and all very old emails are extra copied as mbox or eml using ImportExporttools, then those very old dated archive folders can be deleted saving space.

As Archived emails are stored by year, month and folder name, you could keep the more recent ones available in Local Folders for a period of time.

Any exported backup of an mbox file can be reimported using the ImportExportTool. Any emails stored as .eml files can be opened using Thunderbird without needing to import the .eml files. Although the ImportExportTool can also import them as well. They can be imported to any folder in Local Folders.

re ;His problem will be how to determine which file contains the message(s) that he wishes to review. This may determine the way they should be grouped.

As already mentioned in Archive Options. Select the option to 'Keep folder structure'. Any mbox file which is imported back can be searched in the usual manner via Thunderbird.. Any .eml file, when initially exported as .eml should be saved in a folder of suitable name - perhaps the same name as it was originally stored under. These .eml files can be searched using Windows search if required.

In basic terms. Create Archives folder in Local Folders. Set up Archive options Archive old mail to Archives in Local Folders Create full profile folder backup - store on external drive Delete copies from imap mail account - free up space on server. Export selected folders and/or emails as either mbox files or .eml files. All backups and exported files and/or emails as .eml should be saved to an external storage device. when all is backed up - delete the older archived folders to free up space.

Thanks to both Gild and Toad-Hall for all the details! Based on your responses, here's my plan (and a couple of small remaining questions):

• Create Archives folder in Local Folders.
• Set up Archive options and archive old mail from TB mailbox to Archives in Local Folders
• Create full profile folder backup - store on external drive (to be safe :))
• Delete copies from imap mail account - free up space on server. <- I presume here you mean compact the TB mailbox, since the files should already be off the server since they've been moved to Local Folders
• Export selected folders and/or emails as either mbox files or .eml files. <- To do this, is it okay to just navigate to within my profile and directly copy the Archive folder to an external drive (e.g., Dropbox or a USB drive)? Toad-Hall had mentioned the use of the ImportExportTool add-on - do I need to use this?
• When all is backed up - delete the older archived folders to free up space. <- Is it important to do this from within TB, or can I just delete the associated folders within the profile (i.e., from Finder)?

Thanks again for your help!

Delete copies from imap mail account - free up space on server. <- I presume here you mean compact the TB mailbox, since the files should already be off the server since they've been moved to Local Folders

If using the 'Archive' method then yes, compact folder. If using manual 'copy-to' method, then mnually delete from imap folder and then compact.

Export selected folders and/or emails as either mbox files or .eml files. <- To do this, is it okay to just navigate to within my profile and directly copy the Archive folder to an external drive (e.g., Dropbox or a USB drive)? Toad-Hall had mentioned the use of the ImportExportTool add-on - do I need to use this?

You can manually copy mbox files (they have no extension) directly from the mail account folder in your profile folder. Please be aware that you would discover that there will be an 'Archives' file with no emails. You will also see an 'Archives.sbd' folder, this is used when there are sub folders to an 'Archives' file. Depending upon how many layers of subfolders, this folder may contain emails in mbox files, but it may also contain more *.sbd folders.

The ImportExporttool addon allows you to select specific folder and subfolders in FolderPane and export as mbox files. Saving you from manually locating them. It also allows you to export all the emails in a selected folder as .eml files.

You can select an email and choose 'Save as' and it will save as .eml file, but the addon tool just makes it easier to do this. The ImportExporttool is a useful tool for performing various import and export options. It is not absolutely necessary because you can copy files directly via Profile folders and there is a means of exporting as ,eml using 'save as'.

Some people are comfortable manually locating profile folders and know exactly what they are doing, but some people like a tool that can do it for them. Whether you use it is really down to your preference.

If you need to reimport mbox files then the addon tool is also useful. You would need to reimport mbox files in order to get access to the emails. This is a good means of using as a backup.

Emails saved as individual .eml files can be opened from where they were saved. eml files are usually given the filename using subject, from email address and date. Your computer will recognise the .eml extension and open them in a separate window using Thunderbird. It is also easy to use windows search to search on any aspect of the filename.

The full backup of profile is useful if things go seriously wrong. It will also have all address books, filters, emails in mbox files etc.

I find it useful to save old probably never going to need emails as separate mbox files which can be easily located and imported back if required.

I also save and use eml files for Emails you might/more likely to need access to, but need to store externally and need to be able to easilly search and open without having to import them back into thunderbird. When these become very old, I delete them knowing that I had originally saved them as mbox file. This makes room for newer emails I need to store as eml files.

re : When all is backed up - delete the older archived folders to free up space. <- Is it important to do this from within TB, or can I just delete the associated folders within the profile (i.e., from Finder)?

Easy to do via the Folder Pane. You can delete via Profile folders, but make sure you delete both the mbox file and the .msf indexing file and Thunderbird must be closed before doing it.