SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that allows you to send out messages from your email addresses. Without this, you will not be able to employ email applications or webmail. When you send a message, your SMTP server connects to a DNS server to determine where the e-mails for the recipient domain name are taken care of. Then, it creates a connection to the remote email server and trades information. If the recipient mailbox is accessible, your server transmits the message to the receiving POP/IMAP server and the latter delivers that email to the particular mailbox where the receiver can access it. If you would like to send emails, it is recommended to ensure that the web hosting company offers the service with their plans. Even when you work with an online form that visitors use to contact you, you will still require an active SMTP server for your hosting account for the web form to work.