SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that enables you to send out messages from your email addresses. Without this, you will not be able to use e-mail apps or webmail. Whenever you send an e-mail, your SMTP server creates a connection to a DNS server to find out where the emails for the recipient domain are handled. After that, it creates a connection to the remote email server and exchanges information. If the recipient mail box is accessible, your server transmits the email to the receiving POP/IMAP server and the latter delivers that message to the particular mailbox where the recipient can see it. If you would like to send e-mails, it is recommended to ensure that the website hosting company has the service with their packages. Even though you use an online form that site visitors use to get hold of you, you will still need an active SMTP server for your hosting account for the web form to work.