SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that enables you to send emails from your email addresses. Without it, you will not be able to employ e-mail applications or webmail. When you send an e-mail, your SMTP server creates a connection to a DNS server to determine where the e-mails for the recipient domain name are managed. Then, it creates a connection to the remote email server and trades information. If the recipient mailbox is present, your server transmits the message to the receiving POP/IMAP server and the latter delivers that e-mail to the particular mailbox in which the recipient can see it. If you want to send e-mails, you should always make sure that the website hosting company offers the service with their plans. Even if you make use of online form that visitors use to get hold of you, you still require an active SMTP server for your hosting account for the form to operate.