SMTP, which stands for Simple Mail Transfer Protocol, is the software that enables you to send messages from your email addresses. Without this, you will not be able to employ e-mail applications or webmail. Every time you send a message, your SMTP server creates a connection to a DNS server to determine exactly where emails for the recipient domain name are taken care of. Subsequently, it connects to the remote email server and exchanges details. In case the recipient mailbox is present, your server sends the email to the receiving POP/IMAP server and the latter delivers that message to the specific mailbox where the receiver can get it. If you'd like to send e-mails, you should always ensure that the website hosting company offers the service with their packages. Even when you make use of online form that site visitors use to contact you, you'll still need an active SMTP server for your hosting account for the form to work.