The CommuniGate Pro Server can request a Client Certificate when an external client (a mailer, browser, or a real-time device) establishes a TLS connection with a certain Domain.
Use the WebAdmin Interface to open the Domain Settings page for the target Domain, and click the Security link. The PKI page will appear:
Issued By: Select one of the Trusted Certificates specified for this Domain. When a Trusted Certificate is selected, all TLS clients connecting to this Domain will be requested to present a valid certificate issued by the owner of the selected Trusted Certificate. These certificates can be used for Certificate Authentication.
Required: If this option is selected, only clients presenting valid Certificates can establish TLS connections to this Domain.
The CommuniGate Pro Server processes Client Certificate requests when it establishes a TLS connection to remote servers (SMTP, XMPP, SIP, POP, and other connections). It processes these requests by sending the TLS Certificate assigned to the Main Domain.