MSMQ provides security services that allow applications to authenticate messages using an internal or external certificate. Using an internal certificate allows an application to verify the security identifier (SID) of the user sending the message but nothing more. Using an external certificate allows an application to verify the sender's SID, plus other user information provided in the certificate.
For information on what MSMQ does to authenticate messages, see How MSMQ Authenticates Messages.
For information on using an internal certificate, see Authenticating Messages Using an Internal Certificate.
For information on using an external certificate, see Authenticating Messages Using an External Certificate.