SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that permits you to send e-mails from your email addresses. Without it, 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 determine exactly where e-mails for the recipient domain are handled. Following that, it creates a connection to the remote email server and exchanges information. If the recipient mail box exists, your server sends the e-mail to the receiving POP/IMAP server and the latter brings that e-mail to the particular mailbox in which the receiver can see it. If you would like to send e-mails, it is best to make sure that the web hosting company has the service with their packages. Even if you make use of online form that visitors use to make contact with you, you still need an active SMTP server for your hosting account for the web form to operate.