I got a response from Mailgun within a few hours saying now my domain is enabled. Looks like the domain is active now. Emails to info@pubudu.online are now getting delivered.

The next thing you want after purchasing your new domain is to get an email address with that domain name.

I decided to use Mailgun for that since maintaing your own mail servers is a cumebrsome task. I am not going to create a new Mailgun account since I already have one. You might have to enter your Credit Card information when you register. But you will not be charged untill you send more than 10 000 emails a month.