SMTP, which stands for Simple Mail Transfer Protocol, is the software that enables you to send emails from your email addresses. Without this, you won't be able to use email applications or webmail. When you send an e-mail, your SMTP server creates a connection to a DNS server to learn exactly where e-mails for the recipient domain are handled. Following that, it creates a connection to the remote mail server and exchanges details. In case the recipient mail box is available, your server transmits the email to the receiving POP/IMAP server and the latter delivers that e-mail to the particular mailbox in which the recipient can see it. If you would like to send emails, it is best to make certain that the website hosting company has the service with their plans. Even though you work with an online form that visitors use to make contact with you, you will still require an active SMTP server for your hosting account for the web form to operate.