SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that allows you to send e-mails from your email addresses. Without this, you won't be able to employ e-mail applications or webmail. When you send a message, your SMTP server connects to a DNS server to determine where the emails for the recipient domain name are managed. Then, it creates a connection to the remote mail server and exchanges information. If the recipient mail box exists, your server transmits the email to the receiving POP/IMAP server and the latter brings that message to the specific mailbox in which the recipient can access it. If you want to send emails, it is recommended to make sure that the website hosting company offers the service with their packages. Even when you make use of online form that visitors use to make contact with you, you will still require an active SMTP server for your hosting account for the form to work.