SMTP, which stands for Simple Mail Transfer Protocol, is the software that allows you to send out e-mail messages from your email addresses. Without this, you will not be able to employ email applications or webmail. After you send a message, your SMTP server creates a connection to a DNS server to find out where the e-mails for the recipient domain name are managed. Subsequently, it creates a connection to the remote mail server and exchanges information. In case the recipient mailbox is accessible, your server transmits the e-mail to the receiving POP/IMAP server and the latter brings that message to the specific mailbox where the recipient can access it. If you would like to be able to send e-mails, you should always ensure that the web hosting company provides the service with their packages. Even when you use an online form that site visitors use to get hold of you, you'll still need an active SMTP server for your hosting account for the web form to work.