SMTP, which is short for Simple Mail Transfer Protocol, is the software that allows you to send messages from your email addresses. Without it, you won't be able to use e-mail applications or webmail. After you send a message, your SMTP server connects to a DNS server to determine where the e-mails for the recipient domain name are handled. Then, it connects to the remote mail server and trades details. When the recipient mailbox is accessible, your server sends the e-mail to the receiving POP/IMAP server and the latter delivers that message to the precise mailbox in which the recipient can find it. If you want to be able to send emails, it is recommended to ensure that the hosting company provides the service with their packages. Even if you use an online form that website visitors use to make contact with you, you will still need an active SMTP server for your hosting account for the web form to operate.