SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that allows you to send out emails from your email addresses. Without this, you won't be able to employ e-mail applications or webmail. When you send an email, your SMTP server connects to a DNS server to determine exactly where emails for the recipient domain name are managed. Subsequently, it creates a connection to the remote email server and trades information. When the recipient mailbox is accessible, your server transmits the e-mail to the receiving POP/IMAP server and the latter brings that message to the specific mailbox in which the receiver can get it. If you would like to send emails, it is best to ensure that the hosting company offers the service with their plans. Even when you work with an online form that visitors use to contact you, you'll still need an active SMTP server for your hosting account for the form to work.