If person A has sent a signed e-mail to a DME user at any point in time and in that way submitted his public key to the DME server, every DME user is able to send an encrypted e-mail to A using the e-mail address registered in A's public certificate. Furthermore, the DME user must have a public key stored on the DME server. This is required for the user to be able to store an encrypted e-mail in his own Sent box.
The process of sending encrypted e-mails can be illustrated as follows.
User B uses myDME to upload his personal certificate, if he has not already done so.
User B sends an e-mail to person A from his device, marked as encrypted, and synchronizes his device.
Before delivering the e-mail to the collaboration system, DME verifies both person A and user B have a valid public certificate stored on the server.
If both these conditions are fulfilled, the e-mail is encrypted and passed to the collaboration system. If not, the e-mail is returned to B with an error message specifying the problem.
