apache2 server, postfix, can send emails but cannot receive

I followed the tutorial http://www.tecmint.com/setup-postfix-mail-server-in-ubuntu-debian/.
Everything works fine, except: When I try to send an email from another mail server to my mail server, I get the following error: host said: 550 no such address there.

Such errors occurs when sending email is rejected due to the username unavailability or not found on the system and also there are other common reasons for getting such a “550 No Such Address Here”.

  1. Incorrect or wrong permissions to Mailbox
  2. Sender email address was typed incorrectly.
  3. Mail MX records are not properly configured for the domain.
  4. Wrong routing of Emails.
I suggest you to contact your hosting providers to set correct MX records for the mail domain or hire a server administrator to setup correctly.

Problem solved! MX records were not properly configured