If you wish to send out e-mail messages through an e-mail address with your own domain, you have to make sure that the company will give you access to their SMTP server. The latter is the software that allows email messages to be transmitted. SMTP is an abbreviation for Simple Mail Transfer Protocol and it deals with all outbound e-mails from apps, webmail and contact forms. Whenever a message is sent out, the SMTP server confirms with all of the DNS servers worldwide where the emails for the receiving domain are taken care of and as soon as it acquires this info, it connects to the remote POP/IMAP server to check if the recipient mail box is available. When it does, the SMTP server transmits the message body and so the receiving server delivers it to the mail box where the recipient can open it up and read it. Without having a SMTP server on your server, you will not be capable to mail out emails in any way.