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 won't be able to employ email apps or webmail. Once you send a message, your SMTP server creates a connection to a DNS server to learn exactly where emails for the recipient domain are taken care of. After that, it connects to the remote email server and trades information. In case the recipient mailbox exists, your server transmits the e-mail to the receiving POP/IMAP server and the latter brings that e-mail to the particular mailbox in which the receiver can find it. If you'd like to be able to send emails, you should always make sure that the web hosting company offers the service with their plans. Even if you use an online form that site visitors use to make contact with you, you'll still need an active SMTP server for your hosting account for the web form to operate.