
I did a different thing to add a new domain and the result was like this, I can run:
[ telnet gmail-smtp-in.l.google.com 25 ]
in the terminal to check whether it is open.
The result is like this:
root@telinconetworks:/home/mardo# telnet gmail-smtp-in.l.google.com 25
Trying 74.125.24.27...
Connected to gmail-smtp-in.l.google.com.
Escape character is '^]'.
220 mx.google.com ESMTP 41be03b00d2f7-889e8847ca6si30417228a12.90-gsmtp
451-4.4.2 Timeout - closing connection.
451-4.4.2 For more information, go to
451 4.4.2 https://support.google.com/a/answer/3221692 41be03b00d2f7-889e8847ca6si30417228a12.90-gsmtp
Connection closed by foreign host.
root@telinconetworks:/home/mardo#