I have over 1900 unread emails in my work account. These include Google Scholar alerts I haven’t yet had time to deal look at and other similar content that I will look at when I come to do research that relates to those alerts. My work requires me to subscribe to certain online forums, some days I don’t get to read the content. I also have news subscriptions I often don’t get around to reading. Like @LuckyGuy though, things also get buried before I can file them.
I have to flag things I need to action. My flagged content is up-to-date.
I also don’t like the way Gmail works and I now have to use Gmail for work.