re :or when i have no more access to that specific email account i.e. former job. To my surprise Thunderbird decided at some point to ignore my wishes and ditch my emails for offline use .

A possible reason: If this was an imap account and eg: former employer, deleted emails in your account so removing them off server or possibly moved the emails out of your account into another and then Thunderbird imap account synchronised with empty server because the account itself had not be removed, the imap account would only show what was on server, which would be nothing.

Hyperthetically: If I had a business and an employee ceased to be employed. I would immediately remove emails from the account, but allow imap access to the account knowing it would remove emails from any imap account accessing that server. Those emails may contain business confidentiality information that I was obligued to protect.

No folder in an imap account could ever be considered as a backup or a separate copy on your computer because all imap folders synchronise with server to show a virtual view of server. The imap folders and the server folders are in effect, one and the same.

Hence why, if you think you are no longer going to have access to a server, then you should download full copies and then get copies of all emails put into the 'Local Folders' mail account under suitable folders whilst you still have access to the server. Then the emails are stored on your computer and not in an imap account.

Imap does not work in the same way as POP.

I'm not saying the above possible reason was the cause of loss, but I would put it high on probablity.

Question: Is there deep down some files that have the context of those email so I can recover them?

Only if you have made a backup of the profile or individually saved emails in .eml format in a folder outside of Thunderbird.

Thank you Toad.

However, I'm still looking why my email were not stored locally when I set it stored locally. I noticed that I'm only missing a year. I have mails before and after in this particular account. I wonder because one of the Thundbird update changed the settings or had a bug? I sure did not my change settings! But if that happened how can I trust this client at all?

mozilla69 said

Thank you Toad. However, I'm still looking why my email were not stored locally when I set it stored locally. I noticed that I'm only missing a year. I have mails before and after in this particular account. I wonder because one of the Thundbird update changed the settings or had a bug? I sure did not my change settings! But if that happened how can I trust this client at all?

IMAP stores mail locally only as a cache, not as a local store. Mail must be removed from the IMAP accounts control to become a permanent local storage item. This is inherent in the very definition of the IMAP protocol which everyone uses and basically no one understands fully. Me included.

Toad thank you again for the thoughtful reply. I really appreciate it!

I understand why could that happen on my non-existent account.

However, I'm the curious type, so I just checked my personal account the same issue exists. I own the domain, the server, manage them all. My TB set to sync all folders yet if I go back in time on my inbox folder TB goes to server to fetch email. If I turn off my internet access and check older emails i get the same message "The body of this message has not been downloaded....." , yet i remember reading that email. So somehow TB dumps desktop storage even when it set to keep all message in sync. Is there built-in time limit or disk usage size limit? I look around settings nothing i can find that force all emails be ready on my laptop.

mozilla69 said

However, I'm the curious type, so I just checked my personal account the same issue exists. I own the domain, the server, manage them all. My TB set to sync all folders yet if I go back in time on my inbox folder TB goes to server to fetch email. If I turn off my internet access and check older emails i get the same message "The body of this message has not been downloaded....." , yet i remember reading that email.

Lets look at two thing.

1. if the setting is not to keep messages in the account on this computer in Synchronisation and storage then the email is not ever included in thunderbirds mail storae, the body is downloaded to the cache and this is periodically deleted.

2. If you no longer have access to an email account Thunderbird can not verify the "currency" of the email is has, so random things happen because basically your trying to break a synchronization process that is based in the server copy being canonical.

You can get access to email locked in old IMAP accounts, but it is not always pretty first you have to locate the file the messages are stored in on your hard disk.

The open folder button in Throubleshooting information on the help menu will give you access to file level storage used for your profile. Close Thunderbird. It is never a good idea to meddle with it's profile while it is running. Open the IMAP mail folder in windows file manager. Open the folder named for the mail server the mail is coming from. Here you should see files named after your folders. say inbox and inbox.msf which form the inbox in Thunderbird. the file without the extension has the mail in it. If there is no file, there is no mail. If there is a file copy it out of the profile to some other location. Install the import export tools https://addons.thunderbird.net/en-US/thunderbird/addon/importexporttools-ng/?src=ss

Create a folder in the local folders part of Thunderbird to hold imported mail from the folder and right click it. select the import export option and select to import an mbox file. point it to the file you copied and hopefully it can import any residual mail the file contains without the constraints of IMAP being in the way.

re : I noticed that I'm only missing a year. I have mails before and after in this particular account.

Missing a year is quite precise. Do you have those missing emails in their own folder? Did you 'Archive' a years worth of emails to their own folder?

Please logon to webmail account using a browser. Check through folders just in case those missing emails are in another folder. Maybe they are in a folder which you have not subscribed to see? Do you see those 'missing' emails? If yes, what folder are they in? Have you subscribed to see that folder in Thunderbird?

If yes, in Thunderbird check this: Right click on folder containing missing emails and select 'Properties' select 'Synchronisation' tab Make sure the checkbox 'Select this folder for offline use' is selected. Click on 'Download Now'. click on OK.