Use Postfix Transport Map and Relayhost Map For Flexible Email Delivery

In previous tutorials we discussed how to quickly set up a full-featured mail server using iRedMail or Modoboa, and we also learned how to set up SMTP relay with Postfix SMTP server to bypass port 25 blocking or IP blacklists. However, you might not want to set up your entire email server to use relay host. We can configure Postfix transport map and relay map so that some emails are delivered relay host, other emails are sent directly to recipients.

There are many SMTP relay services. In this tutorial, I use Mailjet, which allows you to send 6000 emails per month for free. SMTP relay services maintain good IP reputation. They stop the bad senders and grow the good ones, so using SMTP relay service will increase the chance of hitting into the inbox.

Read full tutorial here: https://www.linuxbabe.com/mail-server/postfix-transport-map-relay-map-flexible-email-delivery