1. She was unable to use her current folder structure that had been developed and fine-tuned over years of use.

That's expected, because the IMAP server knows nothing about a local folder structure.

3. When I tried to create her account, I tried to move all her messages to the "Local Folders" account,

I'm not sure why. The messages were in the fine-tuned folder structure of the POP account already. I'd hope you did create a backup of the profile folder before this.

and set up IMAP to use these folders.

What does this mean? And what were you trying to achieve with this? It doesn't sound like a good idea to me.

IMAP wanted to synchronize thousands and thousands of e-mail messages, and all her folders, to the mail server.

That's what I meant with 'not a good idea'. You may want to reverse that change.

4. She is legally constrained by both Federal and State law to both preserve and secure her mail data.

Not sure about the legal requirements, but how it sounds to me keeping messages on the server isn't forbidden. The messages will be on the server at some point anyway, and I suppose there is no regulation stipulating for how long. Does 'preserve' mean 'backed up', and 'secure' corresponds to 'local'? If not, what does it mean exactly? You may consider encrypting messages.

On her local system - not a problem. However keeping e-mail stored for extended periods of time on an IMAP server is not a good idea.

I guess it is debatable whether keeping messages on on the server is less secure than keeping messages on the local computer. In any case, with IMAP an offline copy of all messages can be downloaded to the local computer. In Thunderbird this is called Synchronization. https://support.mozilla.org/kb/imap-synchronization

It's the only way I know of to be able to backup messages in an IMAP account.

2. Handle the IMAP interface exactly as if it were a POP-mail interface with ***no messages retained on the server*** after downloading.

Not possible. That's why it's called IMAP, and not POP. What you can do though is to manually move messages off of the server to your local disk to Local Folders. Alternatively you can use the Archive feature. https://support.mozilla.org/kb/archived-messages

The flip side with this is, you may mix up received and sent messages in a single archive folder, which I wouldn't want.

3. Absolutely prevent any messages whatsoever from synchronizing with the upstream mail server.

Not sure what exactly this means. Synchronizing messages with the server is how IMAP works. If you're talking about uploading messages to the server, that would be the case for messages you deliberately copy or move to an IMAP folder.

We already have access to a secure, pass-through, non-logging SMTP mail service, so that's not an issue.

Then you'd probably want to tell Thunderbird not to place a copy of sent messages into the IMAP servers Sent folder.

2. If this is ***not*** possible, can anyone suggest a mail service that allows, and will continue to allow, POP mail service for an extended period of time to come?

I have no suggestion as I'm not using POP. You would probably need to do your own research for a service which fits your needs.

Christ1,

Thanks for your prompt reply!

Let me try to answer your questions:

The legal where and why? That's a question that would take hours to explain properly. Suffice it to say that her system is fully encrypted and requires a smart-card to access. E-mail is queried and removed from the mail server at 10-minute intervals. all connections to both incoming and outgoing mail are encrypted.

Sync: I would need to disable sync. That is, when e-mail messages are read from the server they should be automatically deleted.

I totally understand "that's the way IMAP works" but that's the problem. (grin!) IMAP is designed for the user who has an iPhone, a tablet, stops off at Panera Bread to open chat sessions, and wants to fully integrate his/her Facebook, Instagram, Whatsapp, and Twitter accounts across all the user's devices.

That's OK. Unfortunately, this is not the way it works for my wife. Not only can she not do this, she has absolutely no desire to do this. She doesn't even have a smartphone.

All she wants is an e-mail server that works and a way to access it that works without unnecessary complications.

As far as moving all her messages to her "local folders" account, I was under the impression that messages moved there would automatically *NOT* sync. (they still did - I'm still learning how to configure IMAP.)

I have been researching external mail services, and (so far, as far as I can tell), they fall into one of two broad categories: 1. Fancy "enterprise grade" mail services that are the equivalent of having your own Exchange server. 2. Herky-jerk "consumer" grade stuff like Hotmail or Gmail that have more security vulnerabilities and privacy issues than a mangy dog has fleas.

I guess I'm just stuck.

Jim "JR"

all connections to both incoming and outgoing mail are encrypted.

What I meant was to send and receive encrypted messages in the first place. TLS protected connection to the server is state of the art, but it only protects data in flight. Encrypting the message itself protects data at rest (on the server).

wants to fully integrate his/her Facebook, Instagram, Whatsapp, and Twitter accounts across all the user's devices.

I don't see how social media is related to IMAP email. In general I think IMAP is primarily used in a business or corporate environment, primarily for the features it provides. It may not work for everyone though.

As far as moving all her messages to her "local folders" account, I was under the impression that messages moved there would automatically *NOT* sync.

That's correct. But messages in an existing POP account wouldn't sync to the IMAP server either. So I still have no idea why you'd want to do this.

(they still did - I'm still learning how to configure IMAP.)

I suspect it has something to with 'and set up IMAP to use these folders'. As said before, I don't understand what exactly you did, and why.

2. Herky-jerk "consumer" grade stuff like Hotmail or Gmail that have more security vulnerabilities and privacy issues than a mangy dog has fleas.

I have no idea about Hotmail, and I wouldn't want to use it either. Wrt Gmail, when using all the security measures offered by Google, Gmail is probably one of the most secure email services you can get. It may not be the most private one though.

Wrt privacy, presumably all email services will scan your mail for spam and malware detection. So scanning your mail is not specific to Google, even though they may do things other email providers don't. The only real solution for privacy is to encrypt your messages.

Google is forcing people to turn on "Oauth2" authentication method which is only available in IMAP. I like POP accounts because keeping things on google's server over 6 months is not good hygiene but google security checkup is saying that the "Normal Password" authentication method is not secure. So you must use IMAP to pass the security checkup. I also have developed a rich folder hierarchy in my POP account which would be lost when transitioning to IMAP. Not sure what would happen if i pointed my new IMAP local directory account to the POP account local directory. First issue is that Thunderbird stores IMAP in the ImapMail vs Mail directory. Not sure of any other structural issues. Also am assuming all the POP emails would load to google's servers. Believe the sync issue solves nothing because it just mirrors a local copy of the everything on the server.