SMTP, which stands for Simple Mail Transfer Protocol, is the software that allows you to send emails from your email addresses. Without this, you will not be able to employ e-mail applications or webmail. Whenever you send an email, your SMTP server creates a connection to a DNS server to find out exactly where e-mails for the recipient domain are handled. Following that, it creates a connection to the remote email server and trades details. In case the recipient mail box exists, your server sends the email to the receiving POP/IMAP server and the latter brings that email to the specific mailbox where the receiver can find it. If you wish to be able to send emails, it is best to ensure that the hosting company provides the service with their plans. Even though you use an online form that site visitors use to contact you, you still need an active SMTP server for your hosting account for the web form to operate.