Email root email forward

what do you want to do ? have emails that are set to root user forwarded to your gmail/google app email address ?

Then all you need is to add gmail/google app email to /root/.forward to use server Postfix SMTP.

Postfix is configured for sending out emails for all domains out of box. So you're all taken care of for any site hosted on your server for Postfix outgoing emails sent from the main host name so emails sent from @mainhost.domain.com. Which is why Getting Started Guide step 1 for proper main hostname DNS configuration is important for properly email delivery via Postfix and also mentioned at Email - Steps to ensure your site/server email doesn't end up in spam inboxes | Centmin Mod Community

However, if you use some web hosts like Vultr they block SMTP port by default until you contact support to unblock you for your account - you may need to provide verification ID for them to unblock your SMTP port. They do this to reduce spam. Once unblocked all future Vultr servers created have SMTP unblocked.

 

if you want to setup Postfix relay so all server emails are sent from a 3rd party SMTP server like Sengrid or Amazon SES transactional email, then yes need to follow their postfix relay setup guides. If unsure where a config file is and it was installed via YUM, you can use rpm -ql command to list the YUM packages installed files' locations i.e.

on CentOS 7 postfix yum package list and then grep filter for main.cf to see where it is

Code (Text):

rpm -ql postfix | grep main.cf

you get /etc/postfix/main.cf is the file path

Code (Text):

rpm -ql postfix | grep main.cf
/etc/postfix/main.cf
/usr/libexec/postfix/main.cf
/usr/share/doc/postfix-2.10.1/main.cf.default

• for sendgrid postfix relay https://sendgrid.com/docs/Integrate/Mail_Servers/postfix.html
• for amazon ses postfix relay http://docs.aws.amazon.com/ses/latest/DeveloperGuide/postfix.html