afterscanning all drives with avast home - my Mozilla thunderbird inbox disappeared. did not effect other folders only inbox.
my OS is win xp . the scan found NO problems.
If I’m not wrong, this was reported before.
Problem here is how messages are packed inside of TB inbox and the way antivirus applications work with it :-[ 
Do you have a backup from your inbox? If not, I suggest, now on, you use MozBackup
MozBackup is a utility for creating backups of Mozilla, Mozilla Firefox, Mozilla Thunderbird and Netscape profiles. It allows you to backup mail,
favorites, contacts, etc. http://mozbackup.jasnapaka.com
The Inbox is not ment to store messages, only to receive them in.
Create a seperate box for the messages you want to keep.
And please resize your avatar. It is way to big. (board policy)
Yoy may use this one 
Thanks , I do use MozBackup - Had already backup my emails which included the inbox which has done a runner.
Moderator pse reduce the size of the "never give up " jpg
You should change it by yourself, copying the small gif file (new one posted here) and uploading it into your forum account settings.
Moderators do not work with this
The Moderators don’t do resizing of your avatar that task is yours, however Spyros has kindly done it for you. Right click on the smaller avatar image in his post and save it to your HDD and then use that as your avatar.
Unfortunately you have see first hand that individual infected emails can’t be extracted from a TB email folder. It is not a folder in the true sense of the word with individual files within it but a single file with multiple emails in it. So avast and many other AVs only see an infected file and set off the warning alarm and you must select an option/action.
avast! doesn’t delete automatically unless you have the Pro version and you have set it up to delete. So if it just disappeared with an avast! alarm (no virus detected), etc. then I doubt it is down to avast! The inbox in many email programs is the most vulnerable to corruption and lose because that is the one which is often in use/open.
Thunderbirds own FAQ mentions not to use the inbox for general storage, rather move emails to a more appropriate folder, personal, newsletters, etc. that way if your inbox dies your loss is minimised. Thankfully you have backed up your emails, etc.