Cannot send emails to outside domain

Hello,

              I have a domain configured in route  53. I have whm and cpanel license also. I would like send emails from the cpanel webmail round cube. But right now i am able to send emails within the domain only. Say for example if the domain is abc.com , i can send emails to a@abc.com,b@abc.com etc. But i cant send emails outside this domain like a@gmail.com, b@gmail.com etc. But emails are receiving from all sources without issue. The smtp port restriction also lifted as per amazon. So would like to get a solution on this. Thanks In Advance.