We use it to secure our email system, to cut down on all the bad emails that we would otherwise receive.
The reason for implementing the product was the huge increase in spam and junk mail which occurred when we were adopting these devices. There have been some changes in the way that email is delivered since then, and one or two of the major spam sources have been taken down or prosecuted or jailed. Today, we have less blanket-spam, but we have more targeted phishing emails or spear phishing.
The combination of emails with links that encourage users to give away their user login information can cause problems. When someone's account is compromised it can result in access to our global address list and access to emails that the compromised user may have sent. Therefore, they have details of the format and the style emails that our company uses. We have communication threads that they can take advantage of because they can inject their fake emails into an existing communication thread and try to fool a supplier or client into giving more information or, worst-case, giving money to the wrong person.