I am configuring the notification mailer for a client. When I click on Apply, it takes time and i get the message shown in the picture although there is no error.
Check your email connections.
Your user/pass may be wrong. Your mail host may be wrong. Your server may not solve the hostname of the mail server, so if that s the case , try with ip address.
It could be related with imap or smtp. So check both sides.
Note that: This forum is not a place to ask the problem that is available elsewhere.
Check oracle support for the diagnostics steps. It is not an advance problem, you can solve it by reading oracle support and doing meaningful tests
Check these kind of notes:
How to Test IMAP, POP, SMTP (Doc ID 317307.1)
Read them carefully and speak with your mail server administrator. Your port may be wrong, your mail server may be ssl enabled and so on.
At the bottom line,
Check oracle support, these issues are known issues and they are related with misconfigurations.