There are a few features in Fleep that may help you in managing your emails in Fleep in a way that helps you keep your focus.
Automute - when enabled, Automute automatically mutes all emails that are sent from an email address that is not among your contacts in Fleep. You can read more about Automute on our blog, and find out why our CEO could not have replaced email with Fleep if it weren't for the Automute feature.
You can configure Automute from under your Account preferences:
Labels - in Fleep, you can use Labels to manage which conversations are shown in the conversation list on the left pane, whether the conversations are shown in the Recent and Muted system labels etc. This can be used to filter out all newsletters, or even all emails from your Recent conversation list, if you wish. Read more about what you can do with Labels here.
You can manage your labels from the Manage labels view, which you can find when you click on your profile in the web version of Fleep: