We know exactly what you tell us. So far that is not much.

Missing from where? Did you perhaps move them as some sort of change of years thing?

HI, When I opened my emails on Monday it looked like thunderbird had reverted back to an older version( I am totally innocent I did not do anything!!!) and I had emails in my inbox for January 2024 but all of 2023 is missing , the next email in the inbox is 2022. I tried to repair to no avail. Thunderbird looks like its gone back to the newest version again but alas all my emails from 2023 inbox are still missing. Gremlins are at work!!!!!

• What Operating System do you use? Windows 10 ?
• What Anti-Virus do you use?
• What version of Thunderbird are you currently using?

• Are the missing emails in an Imap or Pop mail account ?
• It sounds like all the emails are stored in one folder called Inbox. Confirm: Are the missing emails gone from only the 'Inbox' or across lots of various folders?
• Did an 'Archive' occur and those missing emails are actually in the 'Archives' folder?

Logon to webmail account via a browser and report on whether the missing emails are on the server.

I have windows 8.1 and Norton antivirus , latest update from thunderbird installed. ?I think its a pop account ( I don't understand the difference) The missing emails were in the inbox, it looks like sent emails from 2023 are also missing. Can't find anything in archives folder Webmail account only goes back to jan 2024 so missing emails aren't on server

re :I think its a pop account ( I don't understand the difference)

'Account Settings' > 'Server Settings' for the account will tell you the 'Server Type'. Pop downloads from server Inbox to pop account Inbox. There is no synchronising between pop account folders and server folders. You can choose to delete emails and not have them deleted off server. Assuming full download and not just headers means emails are stored as independent copies on your computer. Settings can be set up so upon download messages are left on server or auto deleted.

Imap account folders synchronise with server folders to show whatever is held on server. If you delete email via webmail or another imap account that access same mail account then you will find that email auto deleted from the Thunderbird imap account because it does not exist on server. You should not consider emails in an imap account as an independent copy from the server, although you can create a backup. Excellent if you need to access mail using different laptops and phone, but want all of those views to show the same.

re :The missing emails were in the inbox, Do not compact anything.

Check to see if these emails still exist but are marked as deleted and hidden in the mbox file.

• Help > Troubleshooting Information
• Under 'Application Basics' - half way down is Profile Folder - click on 'Open Folder'

A new window opens showing the contents of your profile name folder.

• Exit Thunderbird now - this is important.

• Click on 'Mail' folder to see list of pop accounts and Local Folders.
• Click on the pop mail account name folder to see contents.

The 'Inbox' mbox text file has no extension and contains emails. The 'Inbox.msf' file is an index file used by Thunderbird - it does not store emails.

• Open the 'Inbox' mbox text file using a simple text editor like 'Notepad' or 'Notepad++'

Emails are written to the file one after the other, so oldest will be at the top and newest at the bottom. Each email will start with these lines: this is an example

• From - Sun Dec 28 18:14:40 2014
• X-Mozilla-Status: 0001
• X-Mozilla-Status2: 00800000

It maybe more helpful to scroll to the bottom and then perform a search because you have fewer emails before the missing section.

• Use 'Edit' > 'Find'
• Look for this line: X-Mozilla-Status: (not X-Mozilla-Status2:)
• Choose direction as 'up'
• Click on 'Find Next' and keep working your way up the document.

Hopefully, the emails are still in Inbox, but have been marked as deleted and hidden. check email date - obviously anything that is 2023 needs rescuing.

• Make sure the X-Mozilla-Status: has the number 0001
• Edit that number manually. - see images posted below as a guide.
• Keep checking and perform the above on anything you want to rescue.
• Save the file.
• delete the 'Inbox.msf' file. A new one will be auto created when you start Thunderbird.
• Restart Thunderbird.

Thank you for trying to help I appreciate your assistance.

I followed your instructions but could not find X-Mozilla-Status,nor anything that looked like you described. Under mail, pop account I have inbox with nothing in it and inbox.msf which has gobblegook in it ( probably you understand it!! but it didn't look like what you described)

I think when the Thunderbird update went through on 14/1/2024 the computer was compacting the files and that may have caused the issue???