SMTP, which is short for Simple Mail Transfer Protocol, is the software that permits you to send emails from your email addresses. Without it, you will not be able to use e-mail applications or webmail. Once you send an email, your SMTP server creates a connection to a DNS server to discover where the e-mails for the recipient domain are managed. Following that, it connects to the remote mail server and exchanges information. If the recipient mail box is available, your server sends the email to the receiving POP/IMAP server and the latter brings that message to the precise mailbox where the recipient can get it. If you wish to be able to send emails, you should always ensure that the website hosting company has the service with their plans. Even when you work with an online form that visitors use to make contact with you, you still require an active SMTP server for your hosting account for the web form to function.