Mailbox showing new Unread Item every time user sends new email

Not sure what's happening, already trying to reset Mailbox settings to default, but every time one user sends a new email, her Mailbox registers a new "Unread" message. There can be ZERO unread messages in the Inbox but still showing 1 because of the Sent items issue.

I have read some posts similar to this issue but most are from GW 6.

We are using GW 14 and I am not sure what's causing this to happen. Any suggestions?