SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that enables you to send e-mail messages from your email addresses. Without this, you won't be able to use e-mail apps or webmail. When you send an email, your SMTP server connects to a DNS server to learn where the emails for the recipient domain are handled. After that, it creates a connection to the remote mail server and exchanges information. In case the recipient mail box is available, your server transmits the email to the receiving POP/IMAP server and the latter brings that email to the specific mailbox where the receiver can get it. If you wish to be able to send emails, it is recommended to make sure that the website hosting company offers the service with their packages. Even when you make use of online form that website visitors use to contact you, you still require an active SMTP server for your hosting account for the web form to work.