SMTP, which stands for Simple Mail Transfer Protocol, is the software that allows you to send out messages from your email addresses. Without this, you won't be able to use email apps or webmail. When you send a message, your SMTP server creates a connection to a DNS server to discover exactly where emails for the recipient domain name are managed. After that, it connects to the remote email server and trades information. In case the recipient mailbox is available, your server sends the message to the receiving POP/IMAP server and the latter brings that email to the particular mailbox where the receiver can access it. If you want to be able to send emails, it is recommended to make sure that the hosting company provides the service with their plans. Even though you work with an online form that visitors use to get hold of you, you'll still need an active SMTP server for your hosting account for the form to operate.