SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that enables you to send messages from your email addresses. Without this, you won't be able to use e-mail apps or webmail. After you send a message, your SMTP server creates a connection to a DNS server to determine exactly where emails for the recipient domain are taken care of. After that, it connects to the remote email server and exchanges information. When the recipient mail box is available, your server transmits the email to the receiving POP/IMAP server and the latter brings that message to the precise mailbox where the recipient can access it. If you would like to be able to send emails, it is best to make sure that the website hosting company has the service with their packages. Even if you use an online form that site visitors use to get hold of you, you will still require an active SMTP server for your hosting account for the form to work.