Everyone is talking KMS which is nice but I don't think that is the biggest selling point. Being able to say in which region your email is stored is huge for customers who don't want their data shipped all over the world.
"Another notable feature of WorkMail is that users can specify what Amazon region their e-mail is stored in. Customers can choose a specific, relatively close data center to reduce latency in retrieving e-mail or for compliance purposes—such as European privacy regulations. The feature means that users won’t get the benefit of failover to another data center in the event of an outage, but Amazon may offer mirroring services later."
That is a big differentiator for many companies right there.
http://arstechnica.com/information-technology/2015/01/amazon...
"Another notable feature of WorkMail is that users can specify what Amazon region their e-mail is stored in. Customers can choose a specific, relatively close data center to reduce latency in retrieving e-mail or for compliance purposes—such as European privacy regulations. The feature means that users won’t get the benefit of failover to another data center in the event of an outage, but Amazon may offer mirroring services later."
That is a big differentiator for many companies right there.