Ensure that system scripts can send email

Posted December 23, 2013 4.5k views
What needs to be done to make sure that system scripts are able to send emails to external email addresses when configured to do so?

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3 answers
by Pablo Carranza
Due to the popularity of Gmail, Google Apps,, Yahoo! Mail & a myriad of other providers, many cloud-server users mistakenly fail to install a mail server, initially. However, humans are not the only ones that send electronic mail. If fact, many Linux server applications also need to send email. This tutorial will review how to install a send-only mail server on Ubuntu 12.04.
I did. There's Posfix/Devecot running on the system. Attempts to send emails by system scripts are returning errors, like:

ossec-maild(1223): ERROR: Error Sending email to 5.77.x.y (smtp server) 2013/12/23 15:29:52 os_sendmail(1765): WARN: RCPT TO not accepted by server - ''.

Any clues?
Have you seen this, thread: SMTP timeout?