SMTP, which stands for Simple Mail Transfer Protocol, is the software that enables you to send e-mails from your email addresses. Without this, you won't be able to employ email applications or webmail. Once you send an e-mail, your SMTP server connects to a DNS server to discover exactly where emails for the recipient domain name are taken care of. Then, it connects to the remote mail server and trades information. If the recipient mail box is available, 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 see it. If you want to send emails, you should always make certain that the web hosting company offers the service with their packages. Even when you work with an online form that website visitors use to get hold of you, you'll still need an active SMTP server for your hosting account for the web form to function.