In order for you to send out emails using an email address with your domain, make sure that the company will give you access to their SMTP server. The latter is the software system that permits email messages to be transmitted. SMTP is an acronym for Simple Mail Transfer Protocol and it handles all outbound emails from programs, webmail and contact web forms. Every time a message is sent, the SMTP server confirms with the DNS servers throughout the world where the emails for the receiving domain are managed and when it obtains this info, it creates a connection to the remote POP/IMAP server to check if the recipient mailbox exists. When it does, the SMTP server delivers the message body and the receiving server sends it to the mail box in which the recipient can open it up and read it. Without having a SMTP server on your end, you will not be allowed to mail out emails at all.