SMTP, which stands for Simple Mail Transfer Protocol, is the software that enables you to send out emails from your email addresses. Without it, you won't be able to employ email applications or webmail. Every time you send an e-mail, your SMTP server connects to a DNS server to discover exactly where e-mails for the recipient domain name are managed. Subsequently, it creates a connection to the remote mail server and exchanges information. If the recipient mail box exists, your server sends the email to the receiving POP/IMAP server and the latter brings that message to the particular mailbox in which the receiver can access it. If you would like to be able to send e-mails, it is best to make certain that the website hosting company has the service with their packages. Even if you use an online form that visitors use to get hold of you, you'll still need an active SMTP server for your hosting account for the web form to operate.