Hi Friends,
We are using an Exchange 2013 in our organization. I found that i can use telnet to send mails to internal users without authentication, that is i can send mails using our CEO's mail id to any employee in our organization without authenticating, as we are using a spam filter it is being blocked for external users. Even i can send mails to internal users from: *@gmail.com.
This is a major security issue. My Exchange's receive connector is scoped for 0.0.0.0-255.255.255.255 and i have tried disabling anonymous authentication inDefault Front end connector, but it stopped mail receiving from outside mail systems throwing an :(reason: 530 5.7.1 Client was not authenticated) error.
Please help me to secure the system.