Yahoo Mail Mobile App and Yahoo Web does not synch.
Email(s) read on Yahoo Mobile Application does not seem to be synch with Yahoo Web Application. When logged-In to Yahoo Web, I do see same email I deleted / Moved / Read on Yahoo. Missing synchronization between mobile and web app.
Try removing and re-adding the Yahoo Mail app to your device. If you still find that emails are still showing on the app but not the web, please see this help page for troubleshooting:
Bharat Shah commented
I just connected by google mailbox to Yahoo. Inbox got synched, folders got created but the emails in the folders did not get synched
donna codoni commented
Ditto here! I'm also not receiving new email now on web ap.
Tibor Viga commented
I have the same problem, I am using the desktop web app as well as the mobile app on two devices (iOS and Android). The two mobile apps become synced but any action (read, move, delete) becomes completely out of sync with the web app.