SMTP, which stands for Simple Mail Transfer Protocol, is the software that enables you to send messages from your email addresses. Without it, you will not be able to use e-mail applications or webmail. Once you send a message, your SMTP server creates a connection to a DNS server to find out where the e-mails for the recipient domain name are handled. Following that, it creates a connection to the remote email server and trades information. In case the recipient mail box exists, your server transmits the email to the receiving POP/IMAP server and the latter delivers that e-mail to the specific mailbox where the recipient can get it. If you wish to send e-mails, you should always ensure that the hosting company provides the service with their packages. Even if you make use of online form that visitors use to get hold of you, you'll still require an active SMTP server for your hosting account for the form to work.