SMTP, which is short for Simple Mail Transfer Protocol, is the software that permits you to send emails from your email addresses. Without this, you won't be able to use email apps or webmail. Every time you send an email, your SMTP server connects to a DNS server to discover where the e-mails for the recipient domain name are managed. After that, it connects to the remote mail server and exchanges information. When the recipient mail box is accessible, your server transmits the message to the receiving POP/IMAP server and the latter delivers that email to the particular mailbox in which the recipient can get it. If you wish to send e-mails, it is recommended to ensure that the 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'll still require an active SMTP server for your hosting account for the form to work.