Email Notification with no Email??!

Hi and Tnxs for reading.

On my iOS devices, iPhone and iPad, I got an email notification which is staying there although there is nothing in the incoming folder.

It never happen before. I have the red circle with a marked "1" inside and, the same number shown on the email counter in the email index. However, when selecting the incoming mail folder, it is empty. This is happening on both my iOS devices. I tried to access my yahoo mail via web and no mail are pending.

I tried to disconnect yahoo account from my iOS devices (issue fixed, disappeared), but the notification come back when I reactivate the account.

Any advice please?

Tnxs, cheers.