SMTP, which is short for Simple Mail Transfer Protocol, is the software that allows you to send out e-mail messages from your email addresses. Without this, you will not be able to employ e-mail apps or webmail. Every time you send an e-mail, your SMTP server connects to a DNS server to determine exactly where emails for the recipient domain are managed. Following that, it creates a connection to the remote email server and trades information. If the recipient mail box is available, your server transmits the message to the receiving POP/IMAP server and the latter delivers that email to the particular mailbox where the recipient can get it. If you wish to send emails, you should always make sure that the hosting company provides the service with their packages. Even when you work with an online form that website visitors use to make contact with you, you still need an active SMTP server for your hosting account for the web form to work.