I had the same problem and MailstoreHomePortable gave me the solution. Install the program on both computers and migrate your mails quite easily.

I even have the software and data from the program in a map which syncs with my cloud server. Never lost an e-mail again.

PS Possibly the Mozilla-guys don't like promoting the use of third-party programs but when it works, it works.

You can download it here

Thank you for your reply. I did as you suggested, and I only see an export function. I exported the emails to a profile. How do I import it to my new computer?

So that you know, I attempted to export to an external drive, thinking that I could then import onto the new computer. I received and error message from mailhomestore. I am rather confused as to how I can use this tool, if you would, please let me know what I am doing wrong.

Hi John, I am the person who wrote the Moving Thunderbird Data to a New Computer article, and created the video for it, so I should be able to help. ☺️

There are many steps, so there may be any number of reasons why you're not seeing your inbox messages.

Do you still have access to your old computer? If so, can you please do the following, so we can get more information about your Thunderbird setup:

1. On your old computer, open Thunderbird and go to [=] > Help > Troubleshooting Information then click Copy text to Clipboard.
2. Go to https://paste.mozilla.org/ and go to Edit > Paste to paste the info from your Troubleshooting Information page, then click Paste Snippet.
3. In Firefox, click on the three dots to the right of the address, and select Copy Link.
4. Open a reply to this post, and go to Edit > Paste to paste the link to your troubleshooting information.

I only needed it once, about 2 years ago. I had to move all my mails from a PC to a laptop.

First of all, I put the application as well as the data in a separate map, called MailstoreHome. As you can see in the image, the map is located under Stack01 which is the name of my personal cloud. So when I installed the Stack cloud software on my laptop, it was synchronised and all my mails were transferred.

If you don't have a cloud service of any kind, make a separate map like I did(first pic) where you put the application(and not in the Program Files map or whatever) as well as the data(you can specify this within the program(see the 2nd pic(it's in Dutch but you should recognise the screen))

Then you put that complete map on a USB-stick and copy it to the other computer.

If you use the same mail client on both computers(of course I use Mozilla Thunderbird, otherwise we wouldn't be on this particular help forum), you can bring all your mails back on the 2nd computer by running MailStoreHome from within the map you copied your USB-stick to and opening your personal archive.

On the upper right of that screen you can choose put back in Thunderbird. This you can see in the third pic, again it's in Dutch but you'll recognise it.

This is not the way MailstoreHome would like you to export and or import mails but this way it worked for me, except I didn't need a USB-stick, I just synced with my cloud service on the laptop I mentioned.

I hope this works for you too.

Don't hesitate asking for additional help, or even better: letting me know it worked!!

Now I see @Chris Ilias responded, so you probably won't need my extended explanation anymore how it worked for me(with a third party-program.... ;-) )

I just put in my 2 cents....

For @Chris IIias:

 Application Basics

   Name: Thunderbird
   Version: 60.8.0
   Build ID: 20190703133823

   Update Channel: release
   User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0
   OS: Windows_NT 10.0

   Multiprocess Windows: 0/0 (Disabled)
   Web Content Processes:
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   Enterprise Policies:
   Google Location Service Key: Missing
   Google SafeBrowsing Key: Missing
   Mozilla Location Service Key: Missing
   Safe Mode: false

 Mail and News Accounts
   account1:
     INCOMING: account1, , (none) Local Folders, plain, passwordCleartext

   account2:
     INCOMING: account2, , (pop3) mail.comcast.net:995, SSL, passwordCleartext
     OUTGOING: , smtp.comcast.net:465, SSL, passwordCleartext, true

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Hi John, I noticed that rather than posting your information on paste.mozilla.org, you posted it here. Was that intentional? It makes me wonder if you deviated from the instructions in the article. That could be a clue as to why the instructions didn't work for you.

If all you intend to migrate is your messages, I would recommend using an IMAP account on both machines. With IMAP accounts, the messages and folders are stored on the server, and your email client (i.e. Thunderbird) manages the messages on the server. This allows you to access the same account on more than one device.

In your case, just add the IMAP account to both machines, then drag-and-drop the messages to the IMAP account on your old machine. They should appear in the IMAP account on your new machine, and you can drag-and-drop the messages from there.

Thunderbird defaults to setting up accounts as IMAP, but if you need a new IMAP account, providers such as Gmail can accessed through IMAP.

John wrote

> I can actually see my inbox file underneath my Thunderbird folder in my new PC. I even copied it out, it is about 2.2 GB. Not sure what the problem is?

Like Chris, it's not clear to me why you are not seeing the pop Inbox.

Please post picture of what you are seeing on the old computer, and the new computer, instructions https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem

This first post is a screenshot of the new computer, and you see what level of folder it is. Note that the Inbox is 2.2 GB. Old computer will follow in a new post.

This post is a screen shot of the folders from this old computer. Hope this helps.

Missing in both screen shots is Inbox.msf - fundamental problem. Nothing can be displayed in either Thunderbird if there is not a .msf index file.

I don't know why that would be. Let's see if someone else knows.

Hi John, I noticed that rather than posting your information on paste.mozilla.org, you posted it here. Was that intentional? It makes me wonder if you deviated from the instructions in the article. That could be a clue as to why the instructions didn't work for you.

If all you intend to migrate is your messages, I would recommend using an IMAP account on both machines. With IMAP accounts, the messages and folders are stored on the server, and your email client (i.e. Thunderbird) manages the messages on the server. This allows you to access the same account on more than one device.

In your case, just add the IMAP account to both machines, then drag-and-drop the messages to the IMAP account on your old machine. They should appear in the IMAP account on your new machine, and you can drag-and-drop the messages from there.

Thunderbird defaults to setting up accounts as IMAP, but if you need a new IMAP account, providers such as Gmail can accessed through IMAP.

Chris Ilias said

...If all you intend to migrate is your messages, I would recommend using an IMAP account on both machines. ...

Chris' suggestion may be helpful in the future, but not for the immediate issue of accessing data already in the Inbox. User's popstate.dat is very small for this very large Inbox, suggesting that the user doesn't keep pop mail on the server and so there won't be any history on the server for an imap account to grab.

John, please look in Thunderbird at Inbox in Local Folders. If there is nothing useful there, shut down Thunderbird and copy your Inbox to Mail\Local Folders to replace what is there and delete Inbox.msf if it exists. Then start Thunderbird. Now, do you see at Inbox in Local Folders?

Hi John Start up old computer and start Thunderbird. Is Thunderbird working ok on the old computer? Can you see and read emails in the 'Inbox'?

If yes: Right click on the mail account name in Folder Pane and select 'Settings'. Account Settings window opens. Select 'Server Settings' Bottom right you will see the 'Local directory:' text box. It will start with something like C:\Users\John\AppData\Roaming\...etc The entire line may not show if the window is not wide enough.

Left click on side of window and hold down to grab it, then drag side of window and extend until you can clearly see all the contents of the 'Local directory:' text box with some clear space after it. Please highlight and copy the entire contents of the 'Local directory: text box and paste it into this forum question.