SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that permits you to send out e-mail messages from your email addresses. Without this, you won't be able to employ email apps or webmail. When you send an email, your SMTP server connects to a DNS server to find out where the emails for the recipient domain name are handled. After that, it connects to the remote email server and exchanges details. When the recipient mail box exists, your server transmits the e-mail to the receiving POP/IMAP server and the latter brings that e-mail to the particular mailbox where the recipient can access it. If you'd like to send e-mails, it is best to make certain that the web hosting company provides the service with their packages. Even though you use an online form that site visitors use to make contact with you, you will still need an active SMTP server for your hosting account for the form to function.