If you wish to send out email messages using an email address with your domain name, you have to make sure that the provider will give you usage of their SMTP server. The latter is the software which allows emails to be sent. SMTP is an abbreviation for Simple Mail Transfer Protocol and it deals with all outgoing e-mails from programs, webmail and contact web forms. Every time a message is sent out, the SMTP server checks with all the DNS servers throughout the world where the emails for the receiving domain name are managed and once it gets this info, it will connect into the remote POP/IMAP server to see if the recipient mailbox is available. In case it does, the SMTP server transmits the message body and then the receiving server delivers it to the mail box in which the recipient can open it up and read it. Without having a SMTP server on your server, you will not be allowed to send e-mails at all.