When you've got a shared hosting plan and you create an email address, you might consider the option to send and receive messages for granted, however, this isn't always the case. Sending e-mails isn't always part of the hosting plans that service providers offer and an SMTP service is required to be capable to do that. The abbreviation represents Simple Mail Transfer Protocol and that is the piece of software that allows you to send e-mail messages. If you use an email app, it connects to the SMTP server. The latter then looks up the DNS data of the domain, that is a part of the receiving address to find out which email server manages its e-mails. After system data is swapped, your SMTP server delivers the e-mail to the remote IMAP or POP server and then the e-mail is finally delivered in the related mailbox. An SMTP server is needed if you are using some kind of contact form also, so in case you have a free hosting plan, as an example, it's probable that you won't be able to use this type of form as most free of charge hosting service providers don't allow outgoing emails.