Perhaps a more apropros title here would be:
How I tossed all email clients in the trash and went back to Mac Mail
Not because there is anything wrong with Spark or Airmail. Because there just simply isn't. However, my use case for email has shifted significantly this year.
Previously, mail was a place where recruiters contacted you for bland opportunities. It was a repository for all of those newsletters from the last designery fob purchased. More importantly, it was a productivity black hole, often with no end (this is still unknown for black holes). Leveraging the VIP feature that's been around since iOS6, there is some light at the end of email's uselessness.
Maybe it's just me but, it's often times super hard to keep up with the state of one's GitHub pull requests. It's somewhat hard to know if anyone has responded to your questions (if you have closed the tab that keeps track of unread comments). This leads to a lot of team members going without feedback for extended amounts of time. By assigning the address GitHub uses to email updates to issues and pull requests to a VIP, it receives some special love.
First and formost, all VIP mail gets pushed to a seperate 'inbox section' of Mac Mail. If you are feeling frisky and have your notifications turned on, it will show up in the Notification Center as well. MacOS Sierra also introduced a handy 'filter' feature to Mac Mail. This allows the user to filter their inbox by unread and VIP only users or filter their VIP inbox by unread only.
The combination of VIP's and filters leaves the user with just the very emails that they deem pertinent. In this case, those are emails from GitHub, GitLab or Bitbucket. The ones from your team members responding to pull requests and commenting on issues, pushing a project forward.