Copy the Thunderbird folder from the old computer to the new one:

https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer#thunderbird:mac:tb60

Thank you! I have found that advice on this page. Unfortunately I am not able to do this. .. I guess the reason is that I do not understand how to find those paths and to recognize this folders on my computer (Mac book pro high Sierra on the one Side on the other side Mac book air Mojave). I would probably need a step by step instruction like with pictures. I there anywhere I could call someone? thank you. D

Everything in that link is specifically tailored to a MAC.

What you mean by I do not understand how to find those paths Surely you understand some of those instructions, but maybe get confused at some point, which number in the instructions is causing the confusion?

In Thunderbird, 'Help' is located in two locations - on the 'Menu Bar' toolbar and also in the 'Menu icon (3 lines)' which is on the 'Mail Toolbar'. start on the machine which has all the old data.

1. Click on 'Help' and select 'Troubleshooting Information'. 'Troubleshooting Information' will open in a new tab. 2. Click on 'Show in Finder' button.

A new window automatically opens showing the contents of your Thunderbird 'profile name' folder in Finder. The 'profile name' folder is usually called 'xxxxxxxx.default' where the x's are letters and numbers.

3. Exit Thunderbird. Thunderbird must not be running in order to copy the files and folders.

4 From your Thunderbird profile folder, open the 'Go' menu and select Enclosing Folder two times. This means you need to go up the directory. The 'profile name' folder will be in the 'Profiles' folder. the 'Profiles' folder will be in the 'Thunderbird' folder

You need to copy the 'Thunderbird' folder as mentioned in 5 below. 5. Hold down the control key while you click on the 'Thunderbird' folder, and select Copy "Thunderbird"

Then paste that 'Thunderbird' folder onto a storage device eg: USB or External disk drive etc, so you move it to another computer as described in 6 below. 6. Go to the drive you are using to transfer your data, then hold down the Ctrl key while you click inside the drive, and select Paste Item.

Are you ok so far ?

Hello! I tell you my fault - and it might make you roll with the eyes: i got it wrong which 'Help' to click on. I clicked on the 'Help' on the desktop and not on 'Help' in the program 'thunderbird'. I got the data on my extern drive. Now I am not sure where to place the folder 'thunderbird'. I read the description of 'moving thunderbird data to a new computer' and am not sure if I place the folder in the already existing folder 'thunderbird' on the new computer or under the folder which lays before that and is called 'library'. .. and than I am wondering if all my old e-mails and just appears in thunderbird or what to do to open my old e-mails and to see/get my old folder structure back. - so far: you are my hero for just connecting again although everything was already written detailed. Thank you very much. A.D.

re :I got the data on my extern drive.

That's good.

re :not sure if I place the folder in the already existing folder 'thunderbird'

In new computer.... No....you need to replace that new default 'Thunderbird' folder with the backup 'Thunderbird' folder.

Make sure Thunderbird is closed...it should not be running.

So in 'Library' you will see the 'Thunderbird' folder - this contains the new default profile etc. Paste the backup 'Thunderbird' into the 'Libary' and you should get a pop up asking if you want to 'replace' the Thunderbird folder. You need to click on 'yes'. Alternatively.... Delete that default 'Thunderbird' folder, then paste the backup 'Thunderbird' folder into 'library'.

This means thunderbird will then use the old 'Thunderbird' folder containing all your old emails etc.

then Start Thunderbird.

If your accounts are all set up as IMAP, you can avoid the manual copy of the Thunderbird folder by simply adding the accounts as IMAP to TB on the new computer. Contacts, calendars etc. can be transferred by a simple export-import process. But copying the Thunderbird folder will transfer everything in one step.

Vielen Dank! Thank you very much! It's done - now everything seems very easy. I wish you a very very nice, happy and wonderfull 2019. Thanks.