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 won't be able to employ email applications or webmail. Every time you send a message, your SMTP server connects to a DNS server to discover where the e-mails for the recipient domain are handled. After that, it connects to the remote mail server and trades details. If the recipient mail box is available, your server sends the e-mail to the receiving POP/IMAP server and the latter delivers that message to the particular mailbox in which the receiver can find it. If you would like to send emails, it is best to make sure that the web hosting company provides the service with their plans. Even though you work with an online form that visitors use to get hold of you, you still require an active SMTP server for your hosting account for the form to work.