SMTP, which stands for Simple Mail Transfer Protocol, is the software that enables you to send e-mail messages from your email addresses. Without it, you will not be able to employ e-mail applications or webmail. Once 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 managed. Following that, it creates a connection to the remote email server and exchanges details. When the recipient mailbox is accessible, your server transmits the e-mail to the receiving POP/IMAP server and the latter brings that e-mail to the particular mailbox where the recipient can access it. If you'd like to be able to send emails, you should always ensure that the web hosting company provides the service with their plans. Even when you work with an online form that website visitors use to contact you, you will still need an active SMTP server for your hosting account for the web form to function.