If you wish to send out e-mails through an email address with your own domain, you have to make sure that the provider will give you usage of their SMTP server. The latter is the software that allows e-mails to be dispatched. SMTP is an abbreviation for Simple Mail Transfer Protocol and it addresses all outbound emails from apps, webmail and contact web forms. Every time a message is sent, the SMTP server checks with all the DNS servers globally where the e-mails for the receiving domain name are taken care of and once it gets this data, it creates a connection into the remote POP/IMAP server to see if the recipient mailbox exists. In case it does, the SMTP server transmits the message body and so the receiving server delivers it to the mail box in which the recipient can open it and see it. Without an SMTP server on your server, you will not be able to send messages at all.