Can I get some help with a few issues I am having with an email app?

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AC Question

Two Problems with Email App

I have two issues with the email app. The first is that when I read emails on my tablet, they are seen as read on my desktop and laptop, but not vice-versa. I've looked around in both of my email clients and there doesn't seem to be a way to address this. Secondly, the number count of unread emails, reflected on the tablet's icon, always seems to be reflecting phantom emails that haven't been read. I've scanned through all of my emails and there are none that are unread, despite the app/icon saying there are. This is occurs in both of my most heavily trafficked email addresses. Any assistance would be greatly appreicated. Thanks.