Hi,
I have one CAS 2013 and Mailbox 2013 server. I figured out that relay is open on server and when some from external site try telnet and easily connect with server and send email from external domain and I want to close this at earliest. I have user connect with POP and IMAP which do not use option server authentication required. I want all these POP and IMAP client to connect with server required authetication.
What I believe that this is the main problem that the authentication is not enable on POP IMAP and which applied on telnet as well that open relay for anyone is available for external user
Please guide