Gmail stores all your emails, both sent and received in the 'All Mail' folder and applies 'labels' to each email to faciltate the ability to display emails in a view more like folders. This you see in the gmail webmail account.

gmail imap accounts subscribe to see gmail server folders - aka 'labels'. The imap account folders are in effect one and the same as those on the server. So if you put a copy in two different folders then that is precisely what will occur on the server.

When you put an email in any gmail imap folder (which in Thunderbird is actually stored in an mbox text file assuming it is a fully downloaded copy), there is synchronisation between the imap folder and the server 'folder' and therefore gmail applies the label in order to display in the same way on the server as viewed via webmail.

But all that information is also stated at the link you mention: "When you apply a label to a message in Gmail (That's the webmail account where you may create a new label - aka folder and then put an email in it), Thunderbird creates a folder with the same name as the label and stores the message in that folder. Similarly, if you move a message to a folder in Thunderbird, Gmail will create a label with the folder name and assign it to the message. "

So, whilst Thunderbird does not use 'labels', it does not need to because gmail will apply them automatically in order to display in webmail account.

Naturally, this does not occur if you decide to create a pop account because pop account folders do not synchronise with server folders. They simply download whatever is in server Inbox and put it into the Pop account Inbox.

So, you would need to create an IMAP type of account. Thunderbird by default will auto set up as an imap account.

You need to have cookies enabled in Thunderbird because an imap account uses OAuth2 Authentication Method. So set this up before creating the mail account. In Thunderbird

• Menu app icon > Options/Preferences > Privacy & Security
• Under 'Web Content' section
• Select checkbox 'Accept cookies from sites'

Create the account:

• Menu app icon > New > Existing Mail Account
• Enter name, enter email address, enter password, select checkbox to remember password and then click on 'Continue'.

Thunderbird will auto look for configuration settings and set up as imap. You will get prompted by gmail to logon because gmail want to check you really are you and you want to allow Thunderbird access. Then a token is stored in Thunderbird and fromthen onwards it will be used when connecting with server.

The only special labels that you cannot see in any IMAP account - no matter what email client you use - are the gmail 'Categories', because gmail do not allow it. Seen in webmail account under Settings > Labels, as only specific folders/labels will offer the 'Show in imap' option.

If I were to put an email message in two different folders in Thunderbird, will Gmail know that this is one message that should get two labels.  ?

Yes, you put a copy into another folder in imap folder account and gmail will apply the appropriate label to that message.

Hi Toad-Hall, thanks, but the keyword is here 'copy'. If I copy a message in Gmail browser interface to another folder, no copy is made. It is the same message, just assigned an additional label. In outlook on the other hand: if I copy a message in another folder a copy is made (two messages). When then everything is synced with gmail, there also are 2 messages each with the folder name as a label. But that is not what I want. I want 1 message with two labels. How does thunderbird behave? Thanks.

I'll try again to explain to you that gmail applies the label to the email. There is only one email. In Thunderbird you create a copy to put a copy in another imap folder in order to see it in two places in the Imap account. Synchronisation forces Gmail to apply the relevant label to display that email in two places in webmail view. There is only one copy of the email in the 'All Mail' folder with two labels applied.

In Thunderbird In gmail imap account. Lets say you have an email in 'Inbox'. Lets say you have another folder you created called 'Bills' Let's say you want to see same email in both folders. Right click on the email in Inbox and select 'copy to' and select gmail account 'Bills' folder. A copy appears in the imap 'Bills' folder and the original is still displayed in 'Inbox'

What does this look like in gmail webmail account? In the 'Inbox' folder- aka label, you will see that email and it will have a '[Gmail]/Bills' label displayed just in front of the Subject. In the '[Gmail]/Bills' folder - aka label, you will see that email and it will have a 'Inbox' label displayed just in front of the Subject. Now check the 'All Mail' folder because this is really where Gmail stores everything. There is only the one email stored in 'All Mail' folder, but it has two labels 'Inbox' and [Gmail]/Bills applied by Gmail shown just before the Subject.

So the act of putting a copy in another folder in the imap account in Thunderbird only facilitates seeing that same email in different folders within Thunderbird imap account. It does NOT create another email - a copy - in gmail webmail. There is only the one email which has relevant labels applied to allow display in different folders/labels. It also works the other way around - If you were to access webmail and use the 'Label as' to also see that email in another folder/label in gmail then in Thunderbird you would see same email also appear in the two imap gmail folders. There is synchronisation between the folders in Thunderbird and the Label/folders in Gmail webmail/server.