[twobyfour]

Auto-filter into mailboxes (for instance, one for each type of service that sends notifications).

Each mailbox can typically be gone through rapidly in a batch a couple times per day to get your unreads to zero.

If something requires followup or reply, record that fact in an external system rather than using the inbox as a to do list.

Oh, and get your colleagues to move away from email as a default medium for conversations.