SMTP, which stands for Simple Mail Transfer Protocol, is the software that enables you to send e-mail messages from your email addresses. Without this, you won't be able to employ email apps or webmail. After you send an e-mail, your SMTP server creates a connection to a DNS server to discover where the e-mails for the recipient domain name are handled. After that, it connects to the remote email server and exchanges details. In case the recipient mailbox is accessible, your server sends the email to the receiving POP/IMAP server and the latter brings that email to the specific mailbox in which the recipient can get it. If you wish to send emails, it is best to ensure that the website hosting company offers the service with their plans. Even when you use an 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.