FAILURE :E-mail settings saved successfully. But error occurred while trying to check connection with mail server - Problem connecting to mailbox.

FAILURE :E-mail settings saved successfully. But error occurred while trying to check connection with mail server - Problem connecting to mailbox.

Whenever tried to connect to exchange server it throws error as:
FAILURE :E-mail settings saved successfully. But error occurred while trying to check connection with mail server - Problem connecting to mailbox.

Log file shows error as:
[12:46:52:032]|[03-29-2017]|[SYSERR]|[INFO]|[56]|: javax.mail.MessagingException: Network is unreachable: connect;
  nested exception is:
java.net.SocketException: Network is unreachable: connect|


Please help.
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