SMTP, which is an acronym 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 e-mail applications or webmail. Every time you send an email, your SMTP server connects to a DNS server to discover where the emails for the recipient domain are managed. After that, it creates a connection to the remote mail server and trades information. When the recipient mailbox exists, your server transmits the message to the receiving POP/IMAP server and the latter brings that email to the precise mailbox in which the recipient can get it. If you would like to be able to send emails, it is best to make certain that the website hosting company offers the service with their plans. Even if you make use of online form that site visitors use to make contact with you, you'll still need an active SMTP server for your hosting account for the web form to function.