If you need to send out emails using an email address with your own domain, you have to make sure that the company will give you usage of their SMTP server. The latter is the software which permits e-mail messages to be sent out. SMTP is an acronym for Simple Mail Transfer Protocol and it manages all outgoing e-mails from applications, webmail and contact forms. Whenever a message is sent out, the SMTP server checks with the DNS servers globally where the emails for the receiving domain name are taken care of and as soon as it acquires this information, it creates a connection into the remote POP/IMAP server to find out if the recipient mail box exists. In case it does, the SMTP server transmits the email body and so the receiving server delivers it to the mailbox where the recipient can open it up and read it. Without an SMTP server on your end, you will not be able to mail out e-mails at all.