SMTP, which stands for Simple Mail Transfer Protocol, is the software that enables you to send messages from your email addresses. Without it, you won't be able to employ e-mail applications or webmail. When you send an email, your SMTP server connects to a DNS server to discover where the emails for the recipient domain name are managed. Then, it creates a connection to the remote email server and exchanges details. When the recipient mailbox is accessible, your server sends the message to the receiving POP/IMAP server and the latter brings that message to the precise mailbox in which the recipient can access it. If you'd like to be able to send e-mails, you should always make sure that the hosting company offers the service with their plans. 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 form to operate.