we have an exchange 2013 deployment. there is a requirement to have secure mail transfer to-and-from our sister company. we have a cisco mail gateway appliance. I am aware that you can create send/receive connectors at both the ends using certificates and can have secure mail delivery. but considering that there is a mail gateway in the middle, do we still make connectors on exchange or will the secure connection will be at the mail gateway level. I am not sure what is the setup on the other side but I have been asked to propose all options for secure mail delivery and I want to be informed about the components on my side when I talk or coordinate with the admins on the other side. will the secure connection initiate and terminate on the exchange servers or at the mail gateway is my question.