SMTP, which is short for Simple Mail Transfer Protocol, is the software that permits you to send out messages from your email addresses. Without this, you won't be able to use email applications or webmail. Every time you send an e-mail, your SMTP server connects to a DNS server to learn where the e-mails for the recipient domain are handled. Following that, it connects to the remote email server and exchanges details. If the recipient mailbox is present, your server sends the message to the receiving POP/IMAP server and the latter brings that e-mail to the particular mailbox in which the receiver can access it. If you would like to be able to send e-mails, it is best to make certain that the website hosting company offers the service with their plans. Even when you make use of online form that visitors use to contact you, you still require an active SMTP server for your hosting account for the web form to operate.