Mail not Sending from local network

[Tattwam]

Hello

I am unable to send emails from my local network. It is saying : Mail sent successfully, but actually I can not receive it (or it might have not sent).
I tried to send mail by opening Roundcube from outside local network, and it worked well.

Do I need to change any configuration settings? (MAC OS X Server 5.0)

Thanks in advance

[SKaero]

Check the mail server logs to see whats happening to the email. If your trying to send a email to the internet from behind a NAT it is likely being blocked as spam.