re : At present, in my Gmail account in Tbird, I have an Inbox and under [Gmail], 3 sub-folders Drafts, Sent Mail and Spam with nothing in any of them.

This tells me you have an imap mail account. Imap mail accounts have folders that synchronise with server (same folders you would see if logged on webmail account). Basically, imap account folders can only display whatever is on the server in those folders. It is best to consider them as one and the same as the server.

gmail understands that putting everything in one folder is not exactly user friendly. So gmail applies 'labels' to those emails in the 'All Mail' folder which allows those emails to be seen in a virtual view of regular normal looking folders eg: Inbox, Sent Mail' etc. When a new mail is accepted onto the server, it gets stored in 'All Mail' and a label called 'Inbox' is applied, so the email can be seen in the 'Inbox' folder. If you send an email then a 'Sent Mail' label is applied so email is displayed int he 'Sent Mail' folder. In the imap account, those are the folders you see.

re: I do not have an All Mail folder in Tbird (I must have deleted it some time ago). The gmail 'All Mail' folder stores all of your emails, incoming, sent, archived - the lot. You subscribe to see it or unsubscribe from seeing it. You do not need to see. It still exists on server storing everything.

re :Can I delete [Gmail] and its 3 subfolders and use the Gmail Inbox as I would any other Inbox for a non-Gmail email address? You are asking for trouble. You cannot delete any of those folders.

The whole purpose of using an imap account is to subscribe to see server folders. Anything you move or delete - the folders synchronise with server to update server. It does not act like a POP account.

re : That is, simply move emails from the Gmail Inbox to the desired folders in Local Folders,

If you 'move' an email from an imap mail account into a folder under 'Local Folders' mail account, it is moved off the server.

or delete them from the Gmail Inbox so they are moved to the Deleted folder under Local Folders. This will not delete them from server, it will only remove the applied label. To delete off the server you need to have emails put into the gmail 'Trash' folder (sometimes the server calls it 'Bin')

Why are you trying to use an imap account and then performing all this messing around with trying to then get all emails off the server?

Why not use a POP account ? Yes, I know this means you still need to periodically access webmail and get rid of emails, but if you do not use the imap folders to delete properly then you will have the same problem.

Explain why you are trying to use an imap account in a way that it simply is not designed to work.

Have you used a gmail POP account before ?

Toad-Hall, thank you so much for a very helpful response. I've numbered my answers to correspond with your sub-headings.

1. Yes, my Gmail account is IMAP and I should have mentioned that. I understand how IMAP accounts work.

2. Thank you -- understood.

3. What sort of trouble? I have no interest in what's on the server, as I never access Gmail webmail. I just want to be able to operate my Gmail account on Thunderbird exactly the same as I do other email accounts in Tbird.

4. Yes, I understand that and am totally fine with it.

5. I'm only interested in deleting it from my Inbox so that it goes into the Deleted folder in Local Folders (at least temporarily, as I cull the Deleted folder regularly). I don't much care whether it's still on the server, as I never go there. I'm not "trying to then get all emails off the server" -- I don't care what happens on the server -- see 3. above. I'm only using IMAP because I was advised to do so when first setting up Gmail in Thunderbird. Most of my other email accounts are POP, so I understand how they work. If I switch to POP, why would I "still need to periodically access webmail and get rid of emails"? Are there any downsides to switching to POP? Happy to do that if it will make my Gmail life easier.

Thank you again in anticipation.

When using an imap account, it is normal to use Delete and send emails to the imap account Trash folder.

If you do not empty that imap Trash folder, then gmail will empty it every 30 days. Because imap account folders synchronise with server folders, they can only display what is on the server, so the imap Trash folder would synchronise with server Trash which is empty, thus imap Trash will get emptied without any intervention from yourself. When you use the imap TRash folder, this also gets the emails deleted from the 'All Mail' folder, which is where all emails are stored. This helps to keep your quota under control.

If you do not use this method of deleting - you are deleting bypassing the imap Trash, then the labels are removed and the email is archived in the 'All Mail' folder.

If you move email from imap to Local Folders, then it will still be on server in 'All Mail' because the Inbox label got removed, so email is archived. I have just tested this and email lost it's label but it is still in the 'All Mail' folder.

Over a period of time, you end up with more and more emails still on server. The server allows a storage quota. When you reach the limit of the quota, the gmail account will not be able to accept new mail onto the server until space is created. You may also discover you cannot send emails as well, because there is no space on server to store it. This would require you to logon to the webmail account and remove them OR subscribe to see the 'All Mail' folder and delete emails into the imap 'TRash' folder.

Just because you have downloaded a full copy which gets written/appended to a mbox file file, does not mean it is a simple move from one file to another file on your computer. When you open or move etc any email in an imap account, there is a communication with the server to update server. Sometimes people have their Anti-Virus set to scan any file that gets opened. I would suggest you do not allow your Anti-virus to scan any file or folder in your Profile name folder.

You would also need to make sure you are downloading full copies and not just headers - this is set up on a per folder basis. If you use filters to move emails on download off the server, it is also possible emails with an attachment may not get moved properly - email gets moved but is lacking the attachment. Sometimes this is to do with the way the server does the download and sometimes it is due to the Anti-Virus scanning incoming files. But it is something people have mentioned- it does not always happen but you should be aware that it has been reported on occasions.

Anything you send using gmail email address will get stored in the gmail 'All Mail' folder and will automatically have a 'Sent Mail' label applied regardless of whether you choose to keep a copy in the 'Local Folders' account.

Gmail do auto empty anything in the server 'Spam' folder, but if you are not keeping an eye on what is in the 'Spam' folder via imap 'Spam' then you may miss emails. Pop accounts have no access to any server folder to see what is on server because pop account folder do not synchronise with server folders.

When Thunderbird is asked to create a mail account, by default, it will look for the Imap settings as this is what the majority of users seem to use. So when creating the mail account, after entering all the required data, click on 'Continue' and then click on 'Stop' OR wait and then click on 'Configure Manually'. You have to choose the Server Type Incoming Protocol as POP and then make sure the settings are correct. For incoming and smtp the 'Authentication Method:' should be 'OAuth2' because gmail is stopping what they deem as less secure 'Normal Password' option.

You could remove the gmail imap account, restart Thunderbird and then create a new > existing mail account and set it up as POP. Then you would have all your accounts working in the same way. You could set up the Pop account to download emails and delete copy of message on server upon download. This is the default action of any pop account unless you select the Account Settings > Server Settings' checkbox 'Leave messages on server'.

Note If you intend to create a Pop account - do check the gmail pop settings via gmail webmail account - 'Settings' > 'Forwarding and Pop/Imap' > 'Pop download' section You may need to make selections before you create the pop account in Thunderbird.

But remember when creating pop in Thunderbird - it now offers OAuth2. This info may not be mentioned in the gmail info, so you do Not have to set up 2-step verification not use an app specific password.

Toad-Hall, thank you again for your very helpful replies, and my apologies for the delay in this reply.

I've decided to use POP rather than IMAP, as that suits my needs better. With a few minor problems along the way (all resolved, I think), it's all now set up in Thunderbird. Gmail webmail still does some pretty weird things, but hopefully I'll work them out as I learn more over time.

One question -- Gmail webmail puts lots of emails in Junk, although (so far) none of them have been junk. Can I be sure that anything labelled Junk in Gmail webmail will nevertheless be downloaded to my Thunderbird Inbox?

re :One question -- Gmail webmail puts lots of emails in Junk, although (so far) none of them have been junk. Can I be sure that anything labelled Junk in Gmail webmail will nevertheless be downloaded to my Thunderbird Inbox?

If you use POP then Thunderbird can only access and download from the server 'Inbox'. That means only emails that have the 'Inbox' label applied.

So it will not have access to anything in any other folder. If gmail auto applies the Spam label to an email, it will display in webmail Spam folder then Thunderbird will not know about it.

Be aware that gmail does auto empty the server Spam and Trash approx every 30 days.

In gmail webmail make sure all 'Inbox' emails are actually in the 'Inbox'. Settings >Inbox Inbox type: DEfault Choose only the 'Primary' option - uncheck all the other categories. Importance markers - No markers.

In gmail webmail account, I wanted to stop emails being marked as Important as I kept missing them. I created a filter. IF email: Doesn't have : qwertyuioppoiuytreewq Click on 'Continue' When a message is an exact match for your search criteria: select: 'Never mark it as important'

But you could also try same technique to see if you can force spam to remain in Inbox. Doesn't have : qwertyuioppoiuytreewq Click on 'Continue' When a message is an exact match for your search criteria: 'Never send it to spam'

....in the hope it stays in Inbox and Thunderbird can then download it. Worth a try. Then it will be up to you to train Thunderbird Junk filter to send emails to Junk. But at least you have control over this.