SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that permits you to send emails from your email addresses. Without this, you won't be able to use email apps or webmail. Every time you send an email, your SMTP server creates a connection to a DNS server to discover where the e-mails for the recipient domain name are managed. Following that, it creates a connection to the remote mail server and exchanges details. When the recipient mail box is accessible, your server sends the message to the receiving POP/IMAP server and the latter brings that email to the specific mailbox in which the recipient can see it. If you would like to send emails, it is best to make certain that the hosting company offers the service with their packages. Even if you use an online form that site visitors use to get hold of you, you still need an active SMTP server for your hosting account for the web form to operate.