SMTP, which is short for Simple Mail Transfer Protocol, is the software that enables you to send e-mails from your email addresses. Without it, you will not be able to employ email apps or webmail. Once you send an email, your SMTP server creates a connection to a DNS server to learn where the emails for the recipient domain name are taken care of. After that, it connects to the remote email server and exchanges information. In case the recipient mailbox exists, your server sends the e-mail to the receiving POP/IMAP server and the latter brings that message to the particular mailbox in which the receiver can find it. If you wish to send e-mails, it is recommended to ensure that the website hosting company has the service with their plans. Even when you work with an online form that website visitors use to contact you, you'll still need an active SMTP server for your hosting account for the web form to operate.