SMTP, which is short for Simple Mail Transfer Protocol, is the software that permits you to send out messages from your email addresses. Without it, you won't be able to use email apps or webmail. Once you send an e-mail, your SMTP server creates a connection to a DNS server to learn exactly where emails for the recipient domain name are taken care of. Subsequently, it connects to the remote mail server and exchanges information. In case the recipient mailbox exists, your server sends the email to the receiving POP/IMAP server and the latter delivers that e-mail to the specific mailbox where the recipient can find it. If you'd like to be able to send emails, it is recommended to ensure that the web hosting company provides the service with their plans. Even if you work with an online form that site visitors use to get hold of you, you will still need an active SMTP server for your hosting account for the form to function.