SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that enables you to send e-mail messages from your email addresses. Without this, you won't be able to use e-mail applications or webmail. When 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. When the recipient mailbox is present, your server sends the message to the receiving POP/IMAP server and the latter brings that message to the precise mailbox in which the receiver can see it. If you wish to be able to send emails, it is best to make sure that the web hosting company offers the service with their packages. Even though you work with an online form that site visitors use to make contact with you, you still require an active SMTP server for your hosting account for the web form to work.