Once you remove a mail account, then all folders will be removed as there is no means of sychronising with server if account does not exist. Imap emails are stored on server and you see a remote view of emails on server. To see emails in various server folders you need to subscribe to see them. Right click on mail account name in Folder pane and select 'Subscribe'.

re :my all OLD folder If this is a folder on the server, you need to subscribe to see it.

I have a gmail account and you have to select which folders you want to be allowed access using imap via the webmail account and then in Thunderbird subscribe to see them. Maybe this is the same for you.

Actually my thunderbird was having so many mails from 2007 to 2016, but from 2007 to 2014 are only in my thunderbird not in server, and from 2014 to 2016 are available in server. After reconfiguration of e-mail account I can see mail from 2014 to 2016 only. Is there any possibility to get mails from 207 to 2014, is it be available in default folder ?

re : but from 2007 to 2014 are only in my thunderbird not in server,

If you used a pop mail account previously then they would have been on your computer in that pop mail account or if you had moved them into 'Local Folder's' mail account.

Prior to deleting the original mail account, what type of mail account did you have was it pop or imap ? You say previously also we are using IMAP, but if that was the case then those folders and emails would be on the server because imap accounts store emails on server. They would only be stored in Thunderbird if moved out of imap mail account and put in 'Local Folders' mail account. Where were the emails in the mail account or in 'Local folders' mail account?

Check to see if there is an old mail account still in the profile folder. Make hidden files and folders visible: http://kb.mozillazine.org/Show_hidden_files_and_folders

In Thunderbird 'Help' > 'Troubleshooting Information' click on 'show folder' button

Check all places. For pop or Local folders account: click on 'Mail' folder for imap click on 'ImapMail' folder

You will see a list of mail account names. What do you see? Post image(s) showing what mail accounts you see.

select mail account which is not the current one. do you see any mbox files? mbox files do not have any extension. They will be the same name as the folder they were in when shown in Folder pane. So, if folder name was 'Old' then the mbox file will also be called 'Old'. You can open mbox files using a text editor like Notepad.

If you see emails listed one after the other in an mbox file, they can be imported back to eg: Local Folders and you would be able to see those emails.

Do you see any mail account which contains those missing files containing the missing emails?