SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that permits you to send e-mails from your email addresses. Without it, you won't be able to use e-mail applications or webmail. Whenever you send a message, your SMTP server creates a connection to a DNS server to discover exactly where emails for the recipient domain are managed. Subsequently, it connects to the remote email server and exchanges details. When the recipient mail box is accessible, your server sends the message to the receiving POP/IMAP server and the latter brings that email to the specific mailbox where the recipient can get it. If you wish to send e-mails, it is best to ensure that the website hosting company offers the service with their plans. Even when you work with an online form that site visitors use to contact you, you will still require an active SMTP server for your hosting account for the form to operate.