One of our clients’ email volume was easily in the 2MM+/month range as the company has a large sales force (100k+). Email is a critical component for them. It has to be reliable and timely so that they can effectively message, schedule, and direct those sales folks, often at a moments notice.
I was going to have to do what I feared the most: call customer service (and be on hold FOREVER). But then, I saw it . . . I could request a callback from them.