SMTP, which stands for Simple Mail Transfer Protocol, is the software that allows you to send messages from your email addresses. Without it, you will not be able to employ email apps or webmail. Every time 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 creates a connection to the remote email server and exchanges details. If the recipient mail box is present, your server transmits the e-mail to the receiving POP/IMAP server and the latter brings that email to the precise mailbox in which the recipient can see it. If you would like to send e-mails, you should always make sure that the website hosting company provides the service with their plans. Even if you use an online form that website visitors use to contact you, you will still need an active SMTP server for your hosting account for the form to operate.