Message encryption system

A system includes a plurality of mail encryption gateways and a router. Each mail encryption gateway encrypts email according to an encryption policy of a customer. The router stores a plurality of sender policy framework (SPF) records. The router also receives an email and compares a source IP address of the email with the plurality of SPF records. The router determines that the source IP address corresponds to an SPF record of the plurality of SPF records and in response to that determination, determines that a Simple Mail Transfer Protocol From Field of the email comprises a domain of a cloud provider corresponding to the SPF record. In response to that determination, the router determines that a Multipurpose Internet Mail Extension From Field of the email comprises a domain of a customer and in response to that determination, routes the email to a mail encryption gateway.