I have a permanent a notification saying I have 1 mail. But having checked all my mails there isn't one. Does anyone else have this ............ its so annoying ?

Sort of. I noticed recently that sometimes when I get one of the standard fake emails from a fake account saying how wonderful I am, that even after I delete it, my mailbox continues to say I have an unopened email in it for a very long time. Sometimes for days. Eventually it goes away, so no, I don't have a "forever" condition.

The only thing I can think of, is that perhaps the filters are actually trying harder to keep out spam, and at the same time, some spammer is sending actual STREAMS of fake emails again and again, so that what looks to us like a stuck email notification, is actually a long string of half notices and autodeletions.

But who knows.