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Email setup on the Virtual Appliance

there is Postfix MTA installed and running in the Virtual Appliance, configuration is in /etc/postfix
Configure it as per your company's standards for Linux (CentOS 7)

You can optionally use following 2 methods in case you do not know your standards:

Using Smart Host

Smart Host is an email relay in your internal site which accepts incoming email traffic.
You need to know its name and port where it is listening (25 usually).
Under root:
  • Stop Postfix 
    # systemctl enable postfix.service
# systemctl stop postfix.service
  • Set Smart Host and port 
    # vi /etc/postfix/main.cf

relayhost = mail.your_internal_domain.com:25
  • Start Portfix 
    # systemctl start postfix.service
  • In case of "invalid domain" problem set your hostname in FQDN format (include domain) 
    # vi /etc/postfix/main.cf

myhostname = appliance_hostname.your_internal_domain.com

Using MX DNS records

Postfix finds appropriate email relay server from DNS MX records itself.
Under root:
  • Stop Postfix 
    # systemctl enable postfix.service
# systemctl stop postfix.service
  • Set myhostname to actual Appliance hostname in FQDN format (include domain) 
    # vi /etc/postfix/main.cf

myhostname = appliance_hostname.your_internal_domain.com
  • Start Portfix 
    # systemctl start postfix.service

Test email

Try send out a testing email from cmd line 
$ echo "test message"| mailx -s test your_email@company.com
Check succcess in mail log /var/log/maillog

More info