What exactly is "unsecured app". That is where your whole discussion goes off the rails. If the label was correct it would say. Force using Oauth2.0 Authentication. Instead for their own reasons Google decided they would forceoAuth2.0 as secure and everything else as "less secure". Are they correct. Personally I doubt it.

In the mail space user name and password passed over and encrypted connection is something of a best practice. That is why until Thunderbird implemented oAuth2.0 for IMAP accounts (Gmail do not support their secure protocol for POP mail accounts) there were no desktop mail clients that were not "less secure"

oAuth2.0 is a web protocol not a mail one. So in the case of most mail clients actually using the protocol means they are suddenly writing web browser code. Nothing like getting folk that are not familiar with a security protocol and web browser programing to leave holes. Lucky for Thunderbird we were largely able to leverage the Firefox engine that is built into Thunderbird so no web browser development was required.

So to go back to your original question. Nothing has changed, just gmail have decided they want to relabel things. You account is almost certainly pop and Gmail do not support the use of their self proclaimed secure protocol on PP downloads. You could add your account to Thunderbird again as IMAP and use the oAuth2.0 authentication, but really the improvement in security is so low experts are still arguing if it really exists for mail.

Now as you to acknowledging you are using a "less secure app". I hope you are aware that Google do not guarantee to protect anything anyway. All of the responsibility for everything is and always has been on you. Read their term of use here https://www.google.com/intl/en/policies/terms/

Unless you have a better suggestion, choosing "use unsecure app" leaves me no choice. I have a gmail account and I read and save my email in Thunderbird, works real good, I have mail folders in Thunderbird back to 1999, not even sure what was used to read email then. So for now, unless someone advises otherwise, I will read and save my email in Thunderbird. I have tried to setup IMAP in Thunderbird but do not have the knowledge, ability to do so, mainly because I am afraid to make a mistake and lose all the address, email folders etc. that I have stored in Thunderbird. I will continue to read your articles, I have a lot to learn and I am not as quick as I once was. Thanks God bless James

I notice you say, "You could add your account to Thunderbird again as IMAP and use the oAuth2.0 authentication, but really the improvement in security is so low experts are still arguing if it really exists for mail."

Is this difficult to do? Is there a risk of locking myself out of Gmail or Thunderbird if I make an error?

Can I have my email setup as both POP and IMAP at the same time?

Where can I find instructions to do so? I have a feature on my PC made by Acronis called "Try and Decide" this App allows the installation and changes in the computer to be tried and if not wanted you simply accept or reject the changes, would this work for setting up my email?

Thanks God bless James

re :choosing "use unsecure app" seems to work, but my problem now is that I am verifying that I am using an unsecure app.

No - not an unsecure app. If you have a good strong pasword then all will be just fine. It is just gmail saying it is a 'less' secure method, but that does not mean it is less secure. Gmail want you to use their webmail account via a browser so you can see all their lovely ads etc. However, you use email address and normal password to logon to webmail.

Imap OAuth2 is an authentication method. When setting up the imap account, you logon with usual password, then gmail creates a special identification password which is stored in Thunderbird and is used instead of password.

Gmails '2 step authentication' as opposed to 'less secure apps' is designed for those who use eg: a phone and an email client on a computer. The application password is really making it more secure when using a phone, but if you choose that option then, in that instance, you would also need to create an application specific password to use in Thunderbird instead of normal password. Note: you do not have to use a phone to use that method.

If you continue as you are then every once in a while gmail will probably prompt you to update a password or logon to their webmail account to make sure you really are you; after all gmail would like you to see all the lovely ads etc.

re : I have a feature on my PC made by Acronis called "Try and Decide" this App allows the installation and changes in the computer to be tried and if not wanted you simply accept or reject the changes, would this work for setting up my email?

No. Why? Because you are not installing any application, Thunderbird program is already installed.

re :Can I have my email setup as both POP and IMAP at the same time?

POP mail accounts can only get access to the server Inbox and download emails into the Inbox of pop mail account in Thunderbird. These emails are stored on your computer in your Thunderbird profile in mbox files. You can set up Thunderbird to leave a copy on the server if this is required, but by default the server usually deletes the email after they have been 'popped' and downloaded by you. Any email you send via pop mail account will have the sent email stored in pop mail account 'Sent' folder. It will not be stored on server, so will not be visible in imap 'Sent' folder.

IMAP mail accounts see a remote view of the server. You subscribe to see folders. Usually, headers are downloaded and when you click on an email it is retrieved from the server and stored in a temp folder to faciliate viewing. However, you can choose to download full emails and they will be stored in mbox files in profile. You need to understand that Imap folders are synchronised with server. If you delete email via webmail account, it will be deleted from Thunderbird when imap folders synchronise and if you delete via imap folders in Thunderbird then it will be also deleted off server. So in effect, it is like the server and the imap folders are one and the same.

POP is fine if you only use one computer to access emails; but IMAP is ok as well. IMAP is best suited if you use multiple devices /computers to access emails. To make sure pop and imap work side by side, you would need to make sure the POP mail account Account Settings > Server Settings has selected the option to 'Leave messages on server' otherwise the imap account will not see Inbox emails. The 'Local Folders' mail account can be used as storage from either pop or imap mail accounts. Local Folders mail account does not synchronise with any server. So it is a good place for storing imap mail account emails when needing to release space on server.

But what exactly are you trying to achieve by having both?

POP cannot be swapped to IMAP. POP mail accounts do not synchronise folders with server, IMAP accounts do synchronise folders. They work in entirely different ways.

You would need to create a completely new existing mail account. So you would see two mail accounts in the left Folder pane. Same email address, but one would be POP and the other IMAP.

IMAP would have to be set up as a completely separate mail account. So you would end up with seeing all the same emails in both the pop and the imap Inboxes. If you move emails from server/imap Inbox before the pop mail account has accessed server then the pop mail account may not see those emails because they are no longer in Inbox and therefore cannot be downloaded.

It is possible to move all pop mail account emails into 'Local Folders' mail account and then delete the pop mail account. This means you would still have access to all of those emails. Then create an imap mail account to connect with server for all new emails.

You need to be clear about what you are trying to achieve. Both pop and imap have their own advantages.