Store into specific files those emails which are IMPORTANT but NON-URGENT that means all messages containing some valuable information you can take advantage of but not necessarily at this moment. You’ll have to schedule a time for reading those files later otherwise are going to accumulate until being unmanageable.

Make a wise use of tools such as Evernote to classify these emails and use strategically for later.

This step should take away another 20-30 % of your inbox.