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.
