If you'd like to send out e-mails using an email address with your own domain, you have to make sure that the company will provide you with usage of their SMTP server. The latter is the software allowing e-mails to be sent out. SMTP is an abbreviation for Simple Mail Transfer Protocol and it addresses all outgoing emails from apps, webmail and contact forms. Every time a message is sent, the SMTP server checks with all the DNS servers around the world where the e-mails for the receiving domain are handled and as soon as it gets this information, it will connect into the remote POP/IMAP server to find out if the recipient mailbox is available. In case it does, the SMTP server sends the message body and the receiving server sends it to the mail box in which the recipient can open it and read it. Without having a SMTP server on your end, you will not be able to mail out messages at all.