I've been having niggling problems with BT Yahoo mail for some time now. I use folders to sort my emails and mark emails as unread as a means of identifying those which are pending. I do a search on the last 7 days to check I have moved mail to the correct folder.
I now find that searches do not pick up all the emails. Today's for instance did not pick up either today's or yesterday's emails. Of those it did pick up it showed some as still being in my inbox when I know I had moved them to a folder. It will not allow me to change the status of some of the emails I have previously marked as unread, or rather it does let me but when I refresh the search the status is back to unread.
In the past I have somehow managed to move emails into the trash folder unintentionally. I can't remember the circumstances but this is the situation I fear; that emails have been , or will be, deleted permanently without my knowledge.