well, I try to send email via google 'aspmx.l.google.com' server, port 25. I can send emial, technically. I just have to wait one minute to wait the sending process complete.
Then I try to do telnet to aspmx.l.google.com from my terminal and I found that it tries ipv6 first and then tries ipv4 after ipv6 is timeout.
I believe that is why I need to wait a minute for sending email.
BTW: I am doing it locally.
Does anyone know what is the real problem and how to fix it?
Thanks in advance