SMTP, which is short for Simple Mail Transfer Protocol, is the software that allows you to send out e-mail messages from your email addresses. Without it, you will not be able to use email apps or webmail. After you send an e-mail, your SMTP server creates a connection to a DNS server to discover where the emails for the recipient domain are managed. After that, it connects to the remote email server and trades details. When the recipient mail box is accessible, your server transmits the email to the receiving POP/IMAP server and the latter brings that message to the precise mailbox where the receiver can see it. If you want to send emails, it is best to ensure that the web hosting company has the service with their packages. Even though you make use of online form that visitors use to get hold of you, you still require an active SMTP server for your hosting account for the web form to work.