SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that enables you to send e-mails from your email addresses. Without it, you will not be able to employ email apps or webmail. When 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. Then, it creates a connection to the remote mail server and trades details. When the recipient mail box is available, your server sends the message to the receiving POP/IMAP server and the latter delivers that message to the specific mailbox in which the receiver can find it. If you wish to be able to send e-mails, you should always ensure that the web hosting company offers the service with their packages. Even if you use an online form that website visitors use to make contact with you, you'll still require an active SMTP server for your hosting account for the form to function.