Background info: When you download emails they get written to an mbox text file (not a folder). Emails are written/appended to the text file one after the other, so oldest will be at the top and newest at bottom. When you move or delete emails from the Inbox, those 'moved' emails get 'marked as deleted' and hidden. But the 'Inbox' still has a copy - when you 'compact' the file, a new one gets written and all the good emails - not 'marked as deleted' get copied over to new file. Then the new file replaces the old file. Obviously, the new file is now much smaller.

It is basic good housekeeping to maintain a healthy file structure.

Compacting the folder removes those traces of those 'moved or deleted' emails. Read good info here: https://support.mozilla.org/en-US/kb/compacting-folders https://support.mozilla.org/en-US/kb/compacting-folders-potential-complications

A) ONLINE DELETION ONLY B) OFFLINE DELETION ONLY C) BOTH ONLINE AND OFFLINE DELETION A, B, or C? Yes, I read all of that, and neither that, nor your answer tells me whether or not we are talking about files on the HDD, the Server, or both. I really would like to have the email LOCAL on the HDD, but deleted from the SERVER--except, maybe the last week or so.... NOW, with that said, this USED to be a really simple thing with Thunderbird. There USED to be a switch that said, "When downloading email from the server, delete the mail from the server." (Or something like that.) Now, I do NOT want to experiment and tell it to delete old mail, just to find out that it deletes it from BOTH the server and the Local HDD. I cannot tell from anything that I have found online if those files are ONLINE or LOCAL, or BOTH.

Read the information on compacting - it is talking about emails that have already been deleted. It is a file clean up operation.

AS you mention : "Clean Up ("Expunge") Inbox on Exit" This means you have an IMAP account, because that option is only available for IMAP mail accounts.

IMAP mail account folders can only show what is on server. The imap folders are not independent of the server. They synchronise with the server folders. If you delete an email then it is deleted in IMAP account and deleted off server - consider the IMAP mail account folders and the webmail server folders as one and the same.

If you download full copies then it means you can read emails when in Offline mode because emails have been downloaded and stored in mbox files in your profile.

When you go back to online mode, folders sychronise with server folders. If you had moved emails from one folder to another then this would get updated to the server folders, so they are identical. If you had deleted emails and put them in the Trash, then this would get updated to server and all those emails you had deleted would also get deleted - moved to TRash on the server.

If you had emptied the Trash - then this would get updated to the server and those emails would get removed off the server.

If the server auto empties the TRash - and many server do have this policy, then when IMAP Trash folder synchronises with the empty Trash folder on server, the imap Trash folder will get emptied to match the server.

Compacting is talking about cleaning up the mbox file of copies of emails that have already been moved out of the folder or deleted.

re : I really would like to have the email LOCAL on the HDD, but deleted from the SERVER. You are using an IMAP mail account. If you delete emails off the server then they cannot be displayed in an IMAP mail account because they do not exist.

re : There USED to be a switch that said, "When downloading email from the server, delete the mail from the server."

That option is still available. BUT it is only available for POP mail accounts. POP mail account folder do not synchronise with server. They are independent and emails are stored on your computer. Pop accounts can only access the server Inbox to download mail. They have no access to other server folders.

You can choose to 'Leave messages on server' and 'Until I delete them' If you do not select 'Leave messages on server' option, they emails are auto deleted off the server when they are fully downloaded into the POP Inbox.

The settings to which you refer only affect messages that you have intentionally deleted, marked for deletion, or caused to be deleted by setting a retention period on a folder.

I have had the same email box for a quarter of a century. I've only used Thunderbird for several years. I know that someone said that my account is IMAP and can only show server files. This is simply not true:

1) IF I totally disconnect from the internet, I can still open Thunderbird and view messages that were downloaded to the HDD (work off-line)...whereas "normal yahoo" does NOT allow for such a task.

2) IF the emails being read were ONLY on the server--there would be ZERO HDD space taken up by files...which is not the case.

I really just want to know if the EXPUNGE is A) Local only, B) Server only, or C) Both.

I found a 4 year old thread... Is THIS thread still accurate? https://bugzilla.mozilla.org/show_bug.cgi?id=1429012

If so... then expunging ONLY applies to files that you think you have deleted through Thunderbird, but are still active on the server end (like "Cached mode" in Outlook)??? IF so, I'm waaaay off base and looking in the totally wrong spot.

ooooh... Yahoo supports BOTH IMAP and POP. It seems that on the old PC I had it set up for POP, but on this one it might be set up as IMAP. Can I change this? (Man it seems the more I discover on this, the more confused I am getting...

OK... I think I've got this...maybe. (NERVOUSLY ASKS YET ONE MORE QUESTION) I moved all inbox mail to a local folder--which seemed to do what I was looking for--saved it to the disk statically, not just cached; and deleted it from the server. Now... I have this HUMOUNGOUS file. IF I take that file and save it in another location as well--will that serve as a good backup if this disk should crash, or will there be a time stamp to it that will cause Thunderbird to not open it later in life? OK, two more questions... Is there a way to tell Thunderbird that i want those local folders to be saved, written to, and read from a different location?

OK... I think I've got this...maybe. (NERVOUSLY ASKS YET ONE MORE QUESTION) I moved all inbox mail to a local folder--which seemed to do what I was looking for-

Now you are really getting far removed from your original posting.

From where I am sitting the changes you've made so far don't seem related to compact nor expunge. What is your REAL goal here (which seems to be multiple)? I don't mean the how, I mean WHY do you want to make these changes.

Your question is not showing up for me on the website, but I see it in email, so I'll answer it with another post. Ok, so moving my messages to the HDD and deleting them without deleting them from the HDD has been my concern from the VERY FIRST POST--and reiterated in every single post I made. I just wasn't aware of how difficult it would be (manual movement and recreation my entire email file structure). I've long wanted to clean up my 25+ year old email box, but do not like discarding emails (yes I found a 15 year old email very helpful recently). However, the search function has started to lag out on yahoo--I suspect from the mere size of the folders. So, with search not working--I'd rather have these on disk, clean that server up, and make it easier to clean up the mailbox locally (I hope). Additionally, I do not always have internet access and find myself needing access to my mail. THIS is, at the very best, irritating. So many times I have come close to reducing my poor PC back to the sand from which it came, though I know it is not the PCs fault that this third world country cannot keep internet running for more than 30 seconds at a time, and I am about to move to an even more poorly connected third world country. However, I also have a fear of losing HDDs... so, I want this backed up on several other HDDs, just in case. So now that I have figured out step one... yes I do seem to be moving to an entirely different thread. I think this question can be answered in one quick, yes or no... but... then again I thought the other could have been answered with one quick A, B, or C... but it turns out I was not understanding what I was reading. Maybe I'll just close this thread out and open another for the new question. Thank you for your assistance.

When you 'move' messages from an imap mail account folder into your 'Local Folders' mail account, you are in effect deleting them off the server. So they cannot be displayed in the imap account.

But, you will still need to expunge/compact the imap folder which originally contained the 'moved' emails in order to clean up the mbox file. That part of your original question remains exactly the same as per instructions I stated.

re : So, with search not working--I'd rather have these on disk, clean that server up, and make it easier to clean up the mailbox locally (I hope).

Imap accounts are designed to store emails on the server and provide a view of those server folders in Thunderbird. Imap accounts work in a different way from Pop accounts and maybe using Imap accounts is not the best option for you.

Perhaps it would be easier for you to remove the imap mail account and set it up again as a POP mail account, then all the emails currently in the server Inbox folder will get downloaded into the Pop account folder. You could then choose to not select the Account Settings 'Leave messages on server' so downloaded emails get auto deleted off the server. The POP account set up may be easier for you to understand.

But, as it is inevitable that you will delete some emails or move emails out of the Inbox into other pop account folders for organising them, you will still need to compact folders.

This can be done manually on a per folder basis:

• Right click on folder and select 'compact'.

The 'Drafts', 'Junk' and 'Inbox' will be the folders that need compacting the most often.

To remove the imap account: Right click on imap mail account folder name in Folder Pane and select 'Settings'. Click on 'Account Actions and select 'Remove account'

Exit Thunderbird - wait a short while for background processes to complate and then start Thunderbird. If you have no mail account, Thunderbird should prompt you to create one. If no prompt then select 'Menu app icon' > 'New' > 'Existing mail account' OR if using the 'Menu Bar' at the top - 'File'> 'New' > 'Existing mail account'

Create a new existing mail account for your emails address. Enter name, email address and password. Select the checkbox for Pasword Manager to remember the password Click on 'Continue'. Thunderbird may automatically look for the imap server settings by default, so you need to click on 'Stop' Then select the 'Pop' option and make sure all the server settings are for POP. See useful info :

• https://support.mozilla.org/en-US/kb/changing-imap-pop

You mention 'Yahoo' so this link may be useful:

• https://support.mozilla.org/en-US/kb/thunderbird-and-yahoo

Toad-Hall Thank you for not giving up on me... Thank you all. I know many have said several things, most of which were the same thing said in different ways. This last posting of yours gives me more insight; and better understanding... I'll see what I can do from here. Thank you again! And thank everyone else as well. You're all great.