Is there anything mentioned in the 'Activity Manager' regarding the 'Sent' folder - deleting messages etc? In your 'Anti-virus/firewall' product, if you check it's history, did it quarantine/fix anything to do with any Thunderbird folders? When you see headers but no body, this tells me your Indexing folder thinks something should exist, but it does not mean it actually exists. If anti-virus product scanned folder and located something it did not like, it would effect the whole file with emails, but not the index file. So it sounds like the anti-virus did something to the 'Sent' folder. Repairing the index file will show you exactly what is in the Sent folder. Right click on 'Sent' folder and select 'Properties' click on 'Repair Folder' click on OK Please can you then check your profile folders. In Thunderbird * Help > Troubleshooting Information * click on 'Show folder' button a new window opens showing contents of profile folder name. * '''Close thunderbird now - this is important.''' If POP: * click on 'Mail' folder If IMAP: * click on 'ImapMail' folder * click on mail account name folder You are looking for an mbox file called 'Sent' with no extensions. Open the 'Sent' (no extensions) mbox File using Notepad. Can you see a load of emails written one after the other - especially any with dates prior to 16th Nov? If no: The emails have been lost perhaps due to something scanning folders. This could be anti-virus product or another malware product you have installed. If yes: 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 Use 'Edit' > 'Find' Starting at the top use the look for this line: '''X-Mozilla-Status:''' 0001 Make sure each X-Mozilla-Status: has the number '''0001''' * edit the number as required working down through the document. * Save the file. * delete the 'Sent.msf' file. A new one will be auto created. * Restart Thunderbird.