What is your account type - POP or IMAP?

I don't know yet. If there is a difference in behavior between POP or IMAP, then please let me know which one can do what I was asking about so I can go that route. Thanks for any help.

I don't know yet.

My question referred to your existing ATT/Yahoo account.

If there is a difference in behavior between POP or IMAP,

There certainly is. Now would probably be a good time for you to find out. http://www.lmgtfy.com/?q=what+is+the+difference+between+pop+and+imap

Since to date I haven't used an email reader, I don't know what my ATT/Yahoo account can use (POP - IMAP). I'll be finding that out after I download Thunderbird (based on answers to my questions) and go through the setup procedure.

Perhaps my specific case will be limited, but I'm wondering if Thunderbird has the capability at all (best case scenario) to distinguish between read and unread emails, and whether it can also download sent emails. If I could just get the answer to those questions, that's all I want to know. Your google link doesn't answer those simple questions. Thanks for any answers.

ATT/Yahoo can be configured as an IMAP account. It is up to you to actually select that and make sure.

IMAP accounts are volatile. Local copies of mail only exist as long as the account exists.

The import export tools add-on can export the mails as MBOX files and later re-import them, In the process moving them to a local store that is not volatile. Or if you choose to add the folders to our new IMAP account, upload them to the new server. Given that earthlink offers IMAP. Earthlink only provide 100Mb for your IMAP mail account. So it may fill quickly. they do offer a larger mail space for a larger price. But perhaps local storage will suffice.for your mail account.

As for maintaining the rad unread status and downloading server folders. That is implicit in IMAP. Any mail client with IMAP can do that.

Now I hope you read that information about IMAP s POP. You will find it crops up "A LOT" Here is the same basic information at Earthlink. https://support.earthlink.net/articles/email/imap-email.php Here is me on the Thunderbird Knowledgebase on the same topic. https://support.mozilla.org/en-US/kb/glossary-terms-including-types-accounts

Not having a basic understanding of what IMAP is and what it does is perhaps the greatest cause of people loosing mail. Your questions here make it clear you have no idea how it works and are trying to find out only the bits that interest you by asking questions. While that works. It is prone to long term disappointment. So please talk the time to at least an overview of the IMAP protocol. Just as you have to know where to Petrol goes in a car, or for that matter if it is Petrol or Diesel, or if the tyre is flat do not drive on it and how to change it You need that same sort of high level understanding of IMAP, or the money to pay those that do.

Thanks Matt for that info. I had read a bit about the differences between POP and IMAP, and after seeing that IMAP keeps everything in sync, I figured it probably does what I was asking about... However, all I need to do is download my whole Yahoo mail account, so I can then delete all mail on the Yahoo server and shut it down. If IMAP syncs everything, then I don't want it do also delete all mail on my local computer. So I would probably have to disable IMAP before deleting my Yahoo account. Seems POP is really what I want, but I'm not sure it will preserve read/unread email differences, and I'm not sure anybody can/will answer that. I'm going to set up a Gmail account so I'm no longer tied to any specific ISP thus this will not be an issue in the future. All this is just for a one time download of my Yahoo email account to my computer, and then it's done.

You asked about read state and your sent folder. POP does neither, it just downloads your imbox.

You want IMAP, you just need to backup the local files using the import export tools before you close the account..

Beautiful. Just the answers I was looking for in the first place. I'll try what you suggest and see how it goes.

Thanks again Matt.