SMTP, which stands for Simple Mail Transfer Protocol, is the software that allows you to send out messages from your email addresses. Without it, you won't be able to employ e-mail applications or webmail. When you send an e-mail, your SMTP server connects to a DNS server to discover exactly where e-mails for the recipient domain are handled. Then, it connects to the remote email server and trades information. If the recipient mail box is available, your server transmits the email to the receiving POP/IMAP server and the latter delivers that e-mail to the particular mailbox where the recipient can find it. If you wish to be able to send e-mails, it is best to make certain that the web hosting company provides the service with their packages. Even though you make use of online form that website visitors use to contact you, you will still need an active SMTP server for your hosting account for the web form to function.