SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that allows you to send e-mail messages from your email addresses. Without it, you will not be able to employ e-mail apps or webmail. Whenever you send an e-mail, your SMTP server connects to a DNS server to determine where the emails for the recipient domain name are managed. Then, it creates a connection to the remote email server and trades information. When the recipient mail box is available, your server transmits the message to the receiving POP/IMAP server and the latter delivers that message to the particular mailbox where the receiver can find it. If you want to be able to send e-mails, you should always make certain that the web hosting company has the service with their packages. Even if you make use of online form that site visitors use to contact you, you will still need an active SMTP server for your hosting account for the web form to function.