SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that enables you to send out e-mail messages from your email addresses. Without this, you won't be able to employ email applications or webmail. Once you send an email, your SMTP server creates a connection to a DNS server to determine exactly where e-mails for the recipient domain name are taken care of. Then, it creates a connection to the remote email server and exchanges details. If the recipient mail box is accessible, your server sends the email to the receiving POP/IMAP server and the latter delivers that email to the precise mailbox where the recipient can access it. If you want to be able to send emails, you should always make sure that the hosting company has the service with their packages. Even when you make use of online form that website visitors use to make contact with you, you still require an active SMTP server for your hosting account for the web form to function.