When you've got a shared hosting plan and you set up an e-mail address, you might take the option to send out and receive emails for granted, however, this isn't always the case. Sending e-mails isn't always a part of the hosting plans that companies offer and an SMTP service is necessary to be able to do that. The abbreviation means Simple Mail Transfer Protocol and this is the software application that allows you to send out e-mails. If you use an email application, it connects to the SMTP server. The latter then looks up the DNS data of the domain, which is a part of the receiving address to find out what mail server deals with its e-mails. After system information is exchanged, your SMTP server delivers the email to the remote IMAP or POP server and the e-mail is finally delivered in the matching mailbox. An SMTP server is necessary if you work with some kind of contact page form as well, so in case you work with a cost-free hosting plan, as an example, it is likely that you will not be able to use such a form since many cost-free web hosting service providers don't allow outgoing emails.