Please answer two questions:

• How did you save your old emails?
• Did you delete your old account in Thunderbird?

If you deleted your old account, you won't be able to view emails that were sent to it in Thunderbird unless if you have a backup you can restore them from. But if you saved them to your hard drive, you can view them by opening the .eml files.

@tjohnson:

Hi, I saved my old emails with Thunderbird in IMAP - actually, I do not know if they were really saved, but I used Thunderbird as an e-Mail-client. While having my old contract, I could work with both: on my emails with Thunderbird and with the same emails on the server of my internet provider. Having changed the contract, I could get my "old" emailadress - but trying it now with Thunderbird, there were no emails left, only the adresses by using the "search"-function. And I did not delete any Thunderbird account.

I don´t think that I had copies on my hard drive - but I will look for the .eml files. Thank you for your answer.

Thank you for your detailed answer. I only have experience with POP, which works quite differently than IMAP, so regrettably I can't help you any further, but I'm sure someone else will be able to answer your question.

IMAP email is server based. You use a client like Thunderbird to remotely view your messages on the server. Just installing Thunderbird and viewing those messages did noting to "save" your messages. If you had of moved the messages out of the Inbox of the IMAP server and into a folder under Local Folders then you would have a copy of them on your computer. That is one of the reasons Local Folders exist.. If you no longer have access to the account on the old providers server then your messages are gone. You might plead your case with the old provider and see if there is something that they can do for you.

It would be good to learn how IMAP and POP email works. It might save this problem in the future.