I installed Posifx on Ubuntu 18.4 LT on an amazon EC2 box. After installation and configuration, I was able to send out two emails to my hotmail and another email account. I do received them. However, I can not send any email any more. I check the /var/log/mail.log. It shows the "connection timed out" Error on these sending attempt.
I am confused why I was able to send but later can not. One thing I am not sure, when configuring the /etc/hosts, I did not use a real FQDN, I just give something like hostname.xxx.com because I can not find FQDN on my amazon EC2 box. Does that cause the problem.
I need to send email out when my application status is changed. Does anyone have experience on sending email from Amazon EC2 box?