I used to maintain a zero unread mailbox. At some point I stopped. Email is just a public global todo list, than any one can write to. It's okay not to read them all.
well, I don't care anymore. I just unsubscribe and run sieve filters to get rid of junk mail. That's something I hate with a passion!
I get three seperate emails every single time I purchase something and pay digitally. It's unfeasible to keep a zero inbox.
The only reason my inbox stopped being 100% read as soon as I got an email was because 99% of the email became spam.