If you need to send emails using an e-mail address with your domain name, you have to make sure that the company will give you access to their SMTP server. The latter is the software that enables emails to be sent out. SMTP is an abbreviation for Simple Mail Transfer Protocol and it deals with all outgoing email messages from apps, webmail and contact web forms. Whenever a message is sent out, the SMTP server checks with the DNS servers globally where the e-mails for the receiving domain are taken care of and once it acquires this data, it creates a connection into the remote POP/IMAP server to see if the recipient mailbox exists. If it does, the SMTP server sends the email body and the receiving server delivers it to the mail box in which the recipient can open it up and read it. With no SMTP server on your server, you won't be able to send out e-mails at all.