SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that enables you to send out emails from your email addresses. Without this, you won't be able to use e-mail apps or webmail. Once you send an e-mail, your SMTP server connects to a DNS server to learn where the e-mails for the recipient domain name are taken care of. Then, it connects to the remote email server and trades information. In case the recipient mailbox exists, your server sends the e-mail to the receiving POP/IMAP server and the latter delivers that email to the specific mailbox where the receiver can see it. If you'd like to be able to send emails, it is recommended to make sure that the hosting company offers the service with their plans. Even though you work with an online form that website visitors use to contact you, you'll still require an active SMTP server for your hosting account for the web form to function.