Install on alpha a postfix server.
Configure it to be the mail server of the domain mastersoftwarelibre.com See directives myhostname, mydomain, myorigin
Configure it to make relay for the outgoin mail in smtp.mundo-r.com
Configure it to accept the mail for the domain mastersoftwarelibre.com (see mydestination)
Add an alias in order to make the mail sent to webmaster@mastersoftwarelibre.com be forwarded to your real account (gmail)
Configure it to be the mail server of our network (10.0.0.0/8). It should allow any IP of our internal network to use it as relay without asking password.
Install another postfix on beta and configure it to forward all email to alpha
tail -f /var/log/mail.info
Test tha all works by sending mails from alpha and beta with mailx