SMTP, which stands for Simple Mail Transfer Protocol, is the software that enables you to send e-mails from your email addresses. Without this, you will not be able to use e-mail apps or webmail. After 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 name are taken care of. Then, it creates a connection to the remote mail server and trades information. In case the recipient mailbox exists, your server transmits the email to the receiving POP/IMAP server and the latter brings that email to the precise mailbox in which the receiver can access it. If you want to send e-mails, you should always make certain that the hosting company has the service with their plans. Even when you make use of online form that site visitors use to get hold of you, you still need an active SMTP server for your hosting account for the web form to work.