If you wish to send out email messages through an e-mail address with your own domain name, you have to make sure that the company will provide you with usage of their SMTP server. The latter is the software which allows e-mails to be dispatched. SMTP is an abbreviation for Simple Mail Transfer Protocol and it deals with all outbound emails from apps, webmail and contact web forms. When a message is sent, the SMTP server checks with the DNS servers globally where the emails for the receiving domain are handled and once it obtains this info, it connects into the remote POP/IMAP server to see if the recipient mailbox is available. When it does, the SMTP server directs the e-mail body and the receiving server delivers it to the mail box in which the recipient can open it and read it. Without an SMTP server on your server, you will not be allowed to mail out messages in any way.