SMTP, which stands for Simple Mail Transfer Protocol, is the software that enables you to send out e-mails from your email addresses. Without it, you won't be able to employ e-mail apps or webmail. When you send a message, your SMTP server connects to a DNS server to learn where the e-mails for the recipient domain name are managed. Subsequently, it connects to the remote mail server and trades information. When the recipient mailbox is available, your server sends the email to the receiving POP/IMAP server and the latter brings that e-mail to the precise mailbox where the receiver can see it. If you'd like to send e-mails, you should always make certain that the website hosting company has the service with their packages. Even when you make use of online form that site visitors use to get hold of you, you'll still require an active SMTP server for your hosting account for the web form to work.