It sounds like your mail files are corrupted.

Try to rebuild the index file of the troubled folder. Right-click the folder - Properties - Repair Folder

Note: depending on the corruption this may erase messages from the affected folder which cannot be recovered anymore. This is what possibly already happened to you. In that case you'd need to restore them from a recent backup.

Corruption is often caused by anti-virus software messing with Thunderbird mail files. It is therefore recommended to create an exception for the Thunderbird profile folder, so that the real-time scanner won't attempt to scan the profile with your mail.

For more information on the profile location see http://kb.mozillazine.org/Profile_folder_-_Thunderbird

If I search for these messages they are found and are noted as if they are within the inbox.

Thunderbird Global Search indexes all your messages. What you see when searching is probably the information from the index, not the actual message.

Thanks I will try to repair folder and set up the exception for the virus scan.

Make sure View-Threads is set to All. It sounds like you might have it set to Unread.

Thank You the view threads setting solved the problem

I have this problem too - have repaired the folder and created an exception for Thunderbird in my anti-virus and ensured the threads is set to all but it is still happening. The read messages only disappear when new messages are downloaded to the inbox. They do not appear in the deleted messages folder at all.

I have repaired as suggested. Also checked threads. Ant-virus has been switched off for Thunderbird for ages, but message has still disappeared. It happened to me recently also. Am baffled!

Anne

Anne,

please start a new thread for your problem. Provide as many details as possible. https://support.mozilla.org/en-US/questions/new