We have email providers to send external emails. But for Outlook-driven internal communications, we had no way to: 1) Send a pretty HTML email, 2) track opens and clicks, 3) send to our internal distribution groups (i.e. "All Employees") and 4) send without an opt out link at the bottom (because this isn't marketing, it's internal comms).
Contact Monkey allows us to do all of the above beautifully and easily. Review collected by and hosted on G2.com.