If you want to send email messages using an email address with your own domain name, you have to make sure that the company will give you access to their SMTP server. The latter is the software which allows email messages to be sent out. SMTP is an abbreviation for Simple Mail Transfer Protocol and it deals with all outgoing e-mails from apps, webmail and contact forms. Whenever a message is sent, the SMTP server checks with all the DNS servers worldwide where the emails for the receiving domain name are managed and when it obtains this data, it connects into the remote POP/IMAP server to find out if the recipient mailbox is out there. When it does, the SMTP server transmits the e-mail body and then the receiving server sends it to the mail box where the recipient can open it and see it. Without having a SMTP server on your end, you won't be able to send messages in any way.