I've said it before. I'm terrible at email. Especially when it comes to replying quickly.
Some days I get so many emails that I'll lose track of some older emails and forget to reply to them in a reasonable amount of time.
I went looking for a solution to help with this and found a Chrome extension for Gmail called Reply-Now that adds color coded relative dates to your inbox.
It was almost perfect, but it assumed you should be replying to every email within an hour, which is kind of insane. Using it, my entire inbox was highlighted in red which made it sort of pointless.
Luckily the extension source was available on Github, so I forked it and made a few changes. It will now highlight emails older than a day in orange, 2 days in red, and 4 days in a subtle flashing red. Check it out below: