SMTP, which is short for Simple Mail Transfer Protocol, is the software that permits 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 email, your SMTP server connects to a DNS server to learn where the e-mails for the recipient domain are handled. Then, it creates a connection to the remote email server and exchanges information. In case the recipient mailbox is accessible, your server transmits the e-mail to the receiving POP/IMAP server and the latter brings that email to the specific mailbox where the recipient can see it. If you want to send e-mails, you should always make certain that the web hosting company has the service with their packages. Even though you work with an online form that website visitors use to get hold of you, you will still require an active SMTP server for your hosting account for the web form to work.